Storage interview questions & answers

DAS,NAS,SAN?

DAS : 

In a Direct Attached Storage (DAS) environment, servers connect directly to the disk array typically via a SCSI interface. The same connectivity port on the Disk array cannot be shared between multiple servers. Clients connect to the Servers through the Local Area Network The distance between the Server and the Disk array is governed by the SCSI limitations. With the

advent of Storage Area Networks and Fibre Channel interface, this method of Disk array access is becoming less prevalent.

NAS: 

In a Network Attached Storage (NAS) environment, NAS Devices access the disks in an array via direct connection or through external connectivity. The NAS heads are optimized for file serving. They are setup to export/share file systems. Servers called NAS clients access these file systems over the Local Area Network (LAN) to run applications. The clients connect to these servers also over the LAN.

SAN: 

In a Storage Area Network (SAN) environment, servers access the disk array through a dedicated network designated as SAN in the slide. SAN consists of Fibre Channel switches that provide connectivity between the servers and the disk array. In this model, multiple servers can access the same Fibre Channel port on the disk array. The distance between the server and the

disk array can also be greater than that permitted in a direct attached SCSI environment. Clients communicate with the servers over the Local Area Network (LAN).

  

What is fabric and fabric management?

Ans: A fabric is a virtual space in which all storage nodes communicate with each other over distances. It can be created with a single switch or a group of switches connected together. Each switch contains a unique domain identifier which is used in the address schema of the fabric.

In order to identify the nodes in a fabric, 24-bit fibre channel addressing is used.

Fabric services: When a device logs into a fabric, its information is maintained in a database. The common services found in a fabric are:

􀁹 Login Service

􀁹 Name Service

􀁹 Fabric Controller

􀁹 Management Server

Fabric Management : Monitoring and managing the switches is a daily activity for most SAN administrators. Activities include accessing the specific management software for monitoring purposes and zoning.

What is zoning? What all the different types of zoning?

Ans: There are several configuration layers involved in granting nodes the ability to communicate with each other:

􀁹 Members - Nodes within the SAN which can be included in a zone.

􀁹 Zones - Contains a set of members that can access each other. A port or a node can be members of multiple zones.

􀁹 Zone Sets - A group of zones that can be activated or deactivated as a single entity in either a single unit or a multi-unit fabric. Only one zone set can be active at one time per fabric. Can also be referred to as a Zone Configuration.

In general, zoning can be divided into three categories:

􀁹 WWN zoning - WWN zoning uses the unique identifiers of a node which have been recorded in the switches to either allow or block access A major advantage of WWN zoning is flexibility. The SAN can be re-cabled without having to reconfigure the zone information since the WWN is static to the port.

􀁹 Port zoning - Port zoning uses physical ports to define zones. Access to data is determined by what physical port a node is connected to. Although this method is quite secure, should recabling occur zoning configuration information must be updated.

􀁹 Mixed Zoning – Mixed zoning combines the two methods above. Using mixed zoning allows a specific port to be tied to a node WWN. This is not a typical method.

What is Single HBA Zoning?

Ans: Under single-HBA zoning, each HBA is configured with its own zone. The members of the zone consist of the HBA and one or more storage ports with the volumes that the HBA will use.

Two reasons for Single HBA Zoning include:

􀁹 Cuts down on the reset time for any change made in the state of the fabric.

􀁹 Only the nodes within the same zone will be forced to log back into the fabric after a RSCN (Registered State Change Notification).

What is LUN Masking?

Ans: Device (LUN) Masking ensures that volume access to servers is controlled appropriately. This prevents unauthorized or accidental use in a distributed environment.

A zone set can have multiple host HBAs and a common storage port. LUN Masking prevents multiple hosts from trying to access the same volume presented on the common storage port.

What is iSNS (Internet Storage  Name service)?

Ans: Each Fibre Channel Name Service message has an equivalent iSNS message. This mapping is transparent, allowing iFCP fabrics with iSNS support to provide the same services that Fibre Channel fabrics can.

When an iFCP or iSCSI gateway receives a Name Service ELS, it is directly converted to the equivalent iSNS Name Service message. The gateway intercepts the response and maps any addressing information obtained from queries to its internal address translation table before forwarding the Name Service ELS response to the original Fibre Channel requester.

What is Fiber Channel?

Ans: Fibre channel is a set of standards which define protocols for performing high speed serial data transfer. The standards define a layered model similar to the OSI model found in traditional networking technology. Fibre Channel provides a standard data transport frame into which multiple protocol types can be encapsulated. The addressing scheme used in Fibre Channel switched fabrics will support over 16 million devices in a single fabric.

What is Hot Spare?

Ans: A hot spare is an idle component (often a drive) in a RAID array that becomes a temporary replacement for a failed component.

For example:

The hot spare takes the failed drive’s identity in the array.

Data recovery takes place. How this happens is based on the RAID implementation:

􀁹 If parity was used, data will be rebuilt onto the hot spare from the parity and data on the surviving drives.

􀁹 If mirroring was used, data will be rebuilt using the data from the surviving mirrored drive.

The failed drive is replaced with a new drive at some time later.

One of the following occurs:

􀁹 The hot spare replaces the new drive permanently—meaning that it is no longer a hot spare and a new hot spare must be configured on the system.

􀁹 When the new drive is added to the system, data from the hot spare is copied to the new drive. The hot spare returns to its idle state, ready to replace the next failed drive.

Note: The hot spare drive needs to be large enough to accommodate the data from the failed drive

Hot spare replacement can be:

􀁹 Automatic - when a disk’s recoverable error rates exceed a predetermined threshold, the disk subsystem tries to copy data from the failing disk to a spare one. If this task completes before the damaged disk fails, the subsystem switches to the spare and marks the failing disk unusable. (If not it uses parity or the mirrored disk to recover the data, as appropriate).

􀁹 User initiated - the administrator tells the system when to do the rebuild. This gives the administrator control (e.g., rebuild overnight so as not to degrade system performance), however, the system is vulnerable to another

failure because the hot spare is now unavailable. Some systems implement multiple hot spares to improve availability.

What is Hot Swap?

Ans: Like hot spares, hot swaps enable a system to recover quickly in the event of a failure. With a hot swap the user can replace the failed hardware (such as a controller) without having to shut down the system.

 Data Availability at the host?

Ans:

Multiple HBAs: Redundancy can be implemented using multiple HBAs. HBAs are the host’s connection to the storage subsystem.

Multi-pathing software: Multi-pathing software is a server-resident, availability enhancing, software solution. It utilizes the available HBAs on the server to provide redundant communication paths between host and storage devices. It provides multiple path I/O capabilities and path failover, and may also provide automatic load balancing. This assures uninterrupted data transfers even in the event of a path failure.

Clustering: Clustering uses redundant host systems connected together. In the event that one of the hosts in the cluster fails, its functions will be assumed by the surviving member(s). Cluster members can be configured to transparently take over each others’ workload, with minimal or no impact to the user.

What is HBA?

Ans: The host connects to storage devices using special hardware called a Host Bus Adapter (HBA).

HBAs are generally implemented as either an add-on card or a chip on the motherboard of the

host. The ports on the HBA are the host’s connection to the storage subsystem. There may be

multiple HBAs in a host.

The HBA has the processing capability to handle some storage commands, thereby reducing the

burden on the host CPU.

What is Volume Manager?

Ans: The Volume Manager is an optional intermediate layer between the filesystem and the physical

disks. It can aggregate several smaller disks to form a larger virtual disk and make this virtual

disk visible to higher level programs and applications. It optimizes access to storage and

simplifies the management of storage resources.

Explain raid levels?

Ans:

RAID 0 – Striped Array with no Fault Tolerance

RAID 1 – Disk Mirroring

RAID 0+1 – Striping and Mirroring

RAID 1+0 – Mirroring and Striping

RAID 3 - Parallel Transfer with Dedicated Parity Disk

RAID 4 - Striping with Dedicated Parity Disk

RAID 5 - Independent Disks with Distributed Parity

What is DWDM?

Ans: Dense Wavelength Division Multiplexing (DWDM)

􀁹 DWDM is a technology that puts data from different sources together on an optical fiber with each signal carried on its own separate light wavelength (commonly referred to as a lambda or λ).

􀁹 Up to 32 protected and 64 unprotected separate

wavelengths of data can be multiplexed into a light

stream transmitted on a single optical fiber.

 Explain FCIP, IFCP, ISCSI?

Ans:

• FCIP – TCP/IP based tunneling/encapsulating protocol for connecting/extending Fibre Channel SANs. The entire FC frame is sent over IP links.

• iFCP – Gateway-to-gateway protocol for FCP over IP. Mapping natively in IP across Fibre Channel and IP. An IP-based tunneling protocol for interconnecting Fibre Channel devices together in place of Fibre Channel switches. When iFCP creates the IP packets, it inserts information that is readable by network devices and routable within the IP network. iFCP wraps Fibre Channel data in IP packets but maps IP addresses to individual Fibre Channel ports.

• iSCSI – Native TCP/IP protocol. An IP-based protocol for establishing and managing Connections between IPbased storage devices, hosts, and clients. No Fibre Channel content, but bridging between iSCSI and FC is possible.

What are WWN and WWPN?

Ans:

WWN: All Fibre Channel devices (ports) have 64 bit unique identifiers called World Wide Names (WWN). These WWNs are similar to the MAC address used on a TCP/IP adapter, in that they uniquely identify a device on the network and are burned into the hardware or assigned through software. It is a critical feature, as it used in several configurations used for storage access.

WWPN:However, in order to communicate in the SAN, a port also needs an address. This address is used to transmit data through the SAN from source node to destination node.

What is FC-AL?

Ans: Fibre Channel Arbitrated Loop has a shared bandwidth, distributed topology, and can connect with hubs.

SAN Toplogies?

Ans: SAN Connectivity Topologies

– Point to Point (P-to-P) : Point to Point is a direct connection between two devices.

– Fibre Channel Arbitrated Loop (FC-AL) :  Fibre Channel Arbitrated Loop has a shared bandwidth, distributed topology, and can connect with hubs.

– Fibre Channel Switch Fabric (FC-SW): Fibre Channel Switched Fabric (FC-SW) can have multiple devices connected via switching technologies. Fibre Channel Switched Fabric provides the highest performance and connectivity of the three topologies. A switched fabric provides scalability and dedicated bandwidth between any given pair of inter-connected devices. It uses a 24-bit address (called the Fibre Channel Address) to  route traffic, and can accommodate as many as 15 million devices in a single fabric.

What is a typical storage area network consists of - if we consider it for implementation in a small business setup ?


If we consider any small buisenss following are essentials componets of SAN

- Fabric Switch
- FC Controllers
- JBOD's

Can you briefly explain each of these Storage area components?

Fabric Swictch: It's a device which interconnects multiple network devices .There are swithes starting from 16 port to 32 ports which connect 16 or 32 machine nodes etc.Vendors who manufacture these kind of switches are Brocade, McData.

FC Controllers : These are Data transfer medias they will sit on PCI slots of Server,u can configure Arrays and volumes on it.

JBOD: Just Bunch of Disks is Storage Box,it consists of Enclosure where set of harddrives are hosted in many combinations such SCSI drives,SAS ,FC,SATA.

What is the most critical component in SAN ?
Each component has its own criticality with respect to buisness needs of a company.

How is a SAN managed ?

There are many management softwares used for managing SAN's to name a few

- Santricity
- IBM Tivoli Storage Manager.
- CA Unicenter.
- Veritas Volumemanger.

Which one is the Default ID for SCSI HBA ?

Generally the default ID for SCSI HBA is 7.
SCSI- Small Computer System Interface
HBA - Host Bus Adaptor



How do you install device drivers for the HBA first time during OS installation ?

In some scenarios you are supposed to install Operating System on the drives connected thru SCSI HBA or SCSI RAID Conrollers,but most of the OS'es will not be updated with drivers for those controllers,that time you need to supply drivers externally,if you are installing windows ,you need to press F6 during the installion of OS and provide the driver disk or CD which came along with HBA.
If you are installing linux you need to type "linux dd" for installing any driver.


What is Array ?

Array is a group of Independent physical disks to configure any Volumes or RAID volumes.

Which are the SAN topologies?

Answer :SAN can be connected in 3 types which are mentioned below:
Point to Point topology
FC Arbitrated Loop ( FC :Fibre Channel )
Switched Fabric

Which are the 4 types of SAN architecture types
Answer :Core-edge
Full-Mesh
Partial-Mesh
Cascade

How many minimum drives are required to create R5 ( RAID 5) ?

Answer : You need to have at least 3 disk drives to create R5.

Can you name some of the states of RAID array ?

Answer : There are states of RAID arrays that represent the status of the RAID arrays which are given below
online
Degraded
Rebuilding
Failed

Name the features of SCSI-3 standard ?

Answer : QAS: Quick arbitration and selection
Domain Validation
CRC: Cyclic redundancy check

Can we assign a hot spare to R0 (RAID 0)array?

Answer :No, since R0 is not redundant array, failure of any disks results in failure of the entire array so we cannot rebuild the hot spare for the R0 array.

Can you name some of the available tape media types ?

Answer :There are many types of tape media available to back up the data some of them are
DLT :digital linear tape - technology for tape backup/archive of networks and servers; DLT technology addresses midrange to high-end tape backup requirements.
LTO :linear tape open; a new standard tape format developed by HP, IBM, and Seagate.
AIT :advanced intelligent tape; a helical scan technology developed by Sony for tape backup/archive of networks and servers, specifically addressing midrange to high-end backup requirements.

what is HA ?

Answer : HA High Availability is a technology to achieve failover with very less latency. Its a practical requirement of data centers these days when customers expect the servers to be running 24 hours on all 7 days around the whole 365 days a year - usually referred as 24x7x365. So to achieve this a redundant infrastructure is created to make sure if one database server or if one app server fails there is a replica Database or Appserver ready to takeover the operations. End customer never experiences any outage when there is a HA network infrastructure.

What is virtualization?

Answer :Virtualization is logical representation of physical devices. It is the technique of managing and presenting storage devices and resources functionally, regardless of their physical layout or location.Virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console. Storage virtualization is commonly used in a storage area network (SAN). The management of storage devices can be tedious and time-consuming. Storage virtualization helps the storage administrator perform the tasks of backup, archiving, and recovery more easily, and in less time, by disguising the actual complexity of the SAN.

Symmetrix VMAX - Possible Questions for Interview

What are the major components of Symmetrix VMAX?

System Bay:
VMAX Engines
Matrix Interface Board Enclosure (MIBE)
Power subsystem components
Standby power supplies (SPS)
Service Processor (server, keyboard/video/mouse, UPS).

VMAX Engine:
Symmetrix VMAX systems provide up to eight VMAX Engines within a system bay on standard configurations and up to four VMAX Engines on extended drive loop configurations. Each VMAX Engine includes:
- Two directors that support front-end, back-end and SRDF connections. Each director has:
- 16, 32,or 64 GB of physical memory
- One System Interface board (SIB) that connects the director and the Matrix Interface Board Enclosure (MIBE)
- Two Back End I/O Modules (2 ports, 4 Gb/s) that connect to storage bay drives.
- Two I/ O Module carriers that provide connectivity between each director and the front-end I/O ports. Front End

I/O Modules support:
- Fibre Channel host connectivity (4 ports, 2, 4, or 8 Gb/s)
- Fibre Channel SRDF connectivity (2 ports, 2, 4, 8 Gb/s)
- FICON host connectivity (2 ports, 2, 4, or 8 Gb/s)
- iSCSI host connectivity (2 ports, 1 Gb/s)
- GigE SRDF connectivity.
- Two Management Modules that provide environmental monitoring
- Two VMAX engine power supplies
- Four cooling fans.

Storage Bay:
Disk array enclosures (DAEs)
Power subsystem: PDPs, PDUs, AC connectors
Standby power supply unit (SPS)
Disk array enclosures (DAEs)

Each disk array enclosure contains:
- Two redundant disk array enclosure power /cooling fans
- Two link control card (LCC) modules
- From 5 to 15 drives per direct-attach enclosure
- From 4 to 15 drives per daisy-chain enclosure.

What are the features of VMAX SE?

Supported Disks: 48 to 360 disks
Single V-Max Engine—two directors
FICON, Fibre Channel, iSCSI, Gigabit Ethernet connectivity
Up to 128 GB global memory

What are features of V-MAX?

96 to 2,400 disks, up to 2 PB—three times more usable capacity
One to eight V-Max Engines (16 directors)
Up to 1 TB (512 GB usable) global mirrored memory
Twice the host ports—Fibre Channel, iSCSI, Gigabit Ethernet, FICON connectivity (up to 128 ports*)
Twice the back-end connections for Flash, Fibre Channel, and SATA drives (up to 128 ports)
Quad-core 2.3 GHz processors to provide more than twice the IOPS
Virtual Matrix architecture connects and shares resources across director pairs, providing massive scalability

Explain about Vaulting in VMAX?

Each director pair (2 – odd / even) on the V-Max system will require 200GB of vault space, that is 40 x 5GB chucks of dedicated vault data space
The vault drives are M1 devices with not Raid or mirroring protection
The vault drive cannot to be used by any host and is reserved for the Symmetrix
Vault drives cannot be configured by Timefinder/Snap, virtual or dynamic sparing
The data space created by the vault drives will be almost equivalent to the size of the cache – memory installed on the machine
flash drives, EFD’s cannot be used for vaulting operations
For permanent sparing, 5 vault drives per loop are essential

What are the management tools for Symmetrix VMAX?

Symmetrix Management Console:
The primary interface for managing Symmetrix arrays.

EMC z/OS Storage Manager (EzSM):
An Interactive System Productivity Facility (ISPF) interface that manages Symmetrix system arrays in mainframe environments.

EMC ControlCenter:
An intuitive, browser-based family of products that provides management of the overall storage environment, including multivender storage reporting, monitoring, configuration, and control.

EMC Solutions Enabler SYMCLI:
A library of commands that are entered from a command line or from a script.

EMC SMI-S Provider:
An SMI-compliant interface for EMC Symmetrix and CLARiiON arrays.

What are the supported disk drive types in VMAX?

Symmetrix VMAX systems support Flash, Fibre Channel, and SATA II drives.

What are the features of Enguinity 5874?

Auto-provisioning Groups:
Simplifies provisioning of configurations with alarge number of hosts by allowing the creation of initiator, port and storage groups. Auto-provisioning Groups is especially helpful in large, virtualized server environments that require the availability of many volumes to many host initiators and many storage ports.

Dynamic configuration changes:
Allows the dynamic configuration of BCV and SRDF device attributes. Decreases impact to hosts during BCV and SRDF set and clear operations.

Concurrent configuration changes:
Provides the ability run scripts concurrently instead of serially.

New Management Integration:
New Management Integration features free up host resources and simplify Symmetrix system management by allowing you to:
Load Symmetrix Management Console on the Service Processor
Attach the Service Processor to your network
Open a browser window from any server in the network
Manage the Symmetrix system from anywhere in your enterprise

SRDF Features:
SRDF Extended Distance Protection (SRDF/EDP), Add and remove dynamic devices to SRDF/A (consistency exempt), Two-mirror SRDF Enginuity Consistency Assist (ECA), SRDF/Star with R22 device protection, 250 SRDF group support ,etc..

Tiered storage optimization:
Fully Automated Storage Tiering (FAST) — Reduces cost for performance, saves energy, and simplifies storage tier management by allowing the dynamic allocation of data across storage tiers, based on user defined policies and on the changing performance requirements of the applications.

Enhanced Virtual LUN technology:
Provides the ability to non disruptively change disk and protection type of a logical volume, and allows the migration of open systems, mainframe, and IBM i volumes to unallocated storage, or to existing volume

Virtual Provisioning:

Simplifies storage management:
Improves capacity utilization by allowing the allocation of more storage to than is physically consumed by a host at onset, and is allocated, as needed, from a shared pool.

Automates pool re balancing:
Allows users to nondisruptively balance workloads and extend thin pool capacity, in small increments if required, while maximizing performance and reducing total cost of ownership.

Maximum number of hypers per physical disk in VMAX (Enguinity 5847)?

512

Can we run the concurrent configuration change sessions on VMX?

Yes, each session holds the different configuration change locks.

How many configuration change sessions we can run concurrently on VMAX?

Up to four concurrent configuration change sessions are allowed to run at the same time, when they are non-conflicting. This means that multiple parallel configuration change sessions can run at the same time as long as the changes do not include any conflicts on Device back-end port, Device front-end port and on Device

What is the FAN-OUT ration of VMAX?

512:1

How many mirror position RAID-5 will occupy in VMAX?

One

How many Initiators can be masked to one FA Port in VMAX?

256

Single FA Port can be a member of multiple Port Groups?

Yes.

Which flag has to be enabled before it is member of port group?

ACLX

A device can be a member of multiple storage groups?

Yes

A single HBA can be a member of multiple Initiator groups?

No

How many members can have one Initiator group?

32

What is the maximum meta size in VMAX?

255 member * 240GB hyper = ~60TB

How do you list the reserved devices?

symconfigure -sid "SymID" list -reserved

What are the advantages of Auto-Provisioning Groups?

Eliminates of searching for required storage on arrays
Eliminates the mapping and masking devices which requires separate tasks for each initiator/port combinations.
Eliminates the host interruptions
Eliminates the storage reclamination
Initiators can be dynamically added or removed from initiator groups
Ports can be dynamically added or removed from port groups
Storage can be dynamically added or removed from storage groups

What are the different types of ports can be a member of Initiator group?

Only Fibre and Gig-E ports on front end directors allowed

What are the restrictions of Initiator Group?

Initiator can belongs to only one Initiator Group
Maximum of 32 Initiators contains one initiator group
Initiator groups can be cascaded

What are the steps to replace a faulty HBA?

Findout and Note down the old HBA WWN
symaccess list logins
Swap out the old HBA card with new HBA
Discover the new HBA and note down the WWN
Symaccess discover hba or symaccess list hba
Replace the WWN
symaccess -sid "SymID" replace -wwwn "old_WWN" -new_wwn "new_WWN"
Establish the new alias for the HBA
symaccess discover hba -rename

What are the advantages of Thin Provisioning?

Reduce the amount of allocated but unused physical storage
Avoid over allocation of physical storage to applications
Reduces energy consumption and footprint
Provision independently of physical storage infrastructure
Minimize the challenges of growth and expansion
Simplifies data layout
Saves costs by simplifying procedures to add new storage
Reduces disk contention and enhances performance
Maximize return on investment
Avoides the application interuptions/host downtime.

Can you explain step by step procedure to implement Virtual/Thin Provisioning?

Creating Data Devices:
symconfigure -sid "SymID" -cmd "create dev count=16, config=2-Way-Mir, attribute=datadev, emulation=FBA, size=4602;" commit -v -nop

Creating Thin Pool:
symconfigure -sid "SymID" -cmd "create pool PoolName type=thin;" commit -nop

Adding Data Devices to thin pool:
symconfigure -sid "SymID" -cmd "add dev 10E4:10E5 to pool PoolName type=thin, member_state=ENABLE;" commit -nop

Creating Thin Devices:
symconfigure -sid "SymID" -cmd "create dev count=16, size=4602, emulation=fba, config=TDEV;" commit -nop

Binding Thin devices to Thin Pool:
symconfigure -sid "SymID" -cmd "bind tdev 10F4:10F7 to pool PoolName;" commit -nop

Mapping and Masking TDEVs to host:

What is the status of TDEVs before they bound to thin pool?

Not Ready

How many Thin Pools can we create in a Array?

The number of pools that can be configured in a Symmetrix array is 512.
This is the total number of pools, including Virtual Provisioning thin v pools, SRDF/A Delta Set Extension (DSE) pools, or TimeFinder/Snap pools.

Maximum no. Of data devices in a thin pool?

As many as data devices can be member of a thin pool, however the limit to the number of thin and data devices that can be configured within a Symmetrix system is 64,000.

What are the Thin Pools recommendations when you are adding data devices?

Only data devices may be placed in a thin pool.
The data devices must all have the same emulation.
The data devices must all have the same protection type.
It is recommended that data devices in a pool all reside on drives that have the same rotational speed.
The data devices in the pool should generally be spread across as many DAs and drives of a given speed as possible.
The devices should be evenly spread across the DAs and drives.
The wide striping provided by Virtual Provisioning will spread thin devices evenly across the data devices. The storage administrator must ensure that the data devices are evenly spread across the back end.
It is recommended that all data devices in a pool are of the same size. Using different size devices could result in uneven data distribution.
The data device sizes should be as large as possible to minimize the number of devices required to encompass the desired overall pool capacity.

What are the VMAX Storage Optimization features?

Dynamic Cache Partitioning:
Allows the allocation of portions of cache to specific device groups.

Symmetrix Priority Controls:
Allows the prioritization of read I/O and SRDF/S transfers by host applications.

Symmetrix Optimizer:
Optimizes performance by monitoring access patterns on storage arrays and transparently moving data between storage tiers.

Virtual LUN:
Allows the movement of data between storage tiers.

Fully Automated Storage Tiering (FAST):
provides sophisticated background algorithms that can automate the allocation and relocation of data across storage tiers based on the changing performance of applications.

Storage provisioning with symaccess allows you to create a group of devices, a group of director ports, a group of host initiators, and with one command, associate them in what is called a masking view. Once a masking view exists, devices, ports, and initiators can be easily added or removed from their respective groups.

Can you explain the step by step procedure for creating Auto provisioning Groups?

The steps for creating a masking view are:
Search the environment for Symmetrix devices on each HBA
symaccess discover hba

Create a storage group (one or more devices)
symaccess -sid XXXX create -name StorageGroupName -type storage devs 3250:3350

Create a port group (one or more director/port combinations)
symaccess -sid XXXX create -name PortGroupName -type port -dirport 7E:0,7G:1,8F:0

Create an initiator group (one or more host WWNs or iSCSIs)
symaccess -sid XXXX create -name InitiatorGroupName -type initiator -wwn wwn

Create a masking view containing the storage group, port group, and initiator group.
When a masking view is created, the devices are automatically masked and mapped.
symaccess -sid XXXX create view -name MaskingViewName -sg StorageGroupName -pg PortGroupName -ig InitiatorGroupName

What is purpose FAST (Fully Automated Storage Tiering)?

FAST is Symmetrix software that runs background algorithms continuously analyze the utilization (busy rate) of the Symmetrix array devices.
FAST can move the most-used data to the fastest storage, such as Enterprise Flash Drives, the least-used data to the slowest storage, such as SATA drives, while maintaining the remaining data on Fibre Channel drives, based on user-defined Symmetrix tiers and FAST policies.
The objective of tiered storage is to minimize the cost of storage by putting the right data, on the right Symmetrix tier, at the right time.

How do you configure the symmetrix array for FAST?

By defining symmetrix tiers
By defining FAST Policies
By defining storage groups

Symmetrix DMX - Possible Questions for Interview

Can you explain about DMX Architecture?

The Symmetrix DMX features a high-performance, Direct Matrix Architecture (DMX) supporting up to 128 point-to-point serial connections. Symmetrix DMX technology is distributed across all channel directors, disk directors, and global memory directors in symmetrix DMX systems.

Can you briefly explain about symmetrix series products?

Symmetrix 8000/4 was the first symmetrix to introduce a dual bus arcitecture, providing redundancy in the path to memory.

Symmetrix DMX800 is an incrementally scalable, high-end storage array which features modular disk array enclosures.

Symmetrix Direct Matrix Architecture is storage array technology that employs a matrix of dedicated serial point-to-point connections instead of traditional buses or switches.

Symmetrix DMX2 is a channel director specification for the DMX with faster processors and newer components.

Symmetrix DMX-3 and DMX-4 are the latest technology using redundant global memory and largest capacity.

Can you explain Enginuity release code 5773.79.58?

57 represents the DMX3/4 Hardware
73 represents the microcode family
79 represents the field release level to the microcode
58 represents the field release to the service processor code

52 =Symm4, 55 =Symm5, 56 =DMX/DMX2, 57 =DMX3/4, 58 =VMAX.

How many Cache directors, Front-end directors and Back-end directors we can use in DMX-4?

Cache Directors = 4 Min to 8 Max.
Front-end Directors = up to 12 max.
Back-end Directors = 6 Min to 8 Max.

What are the different types of Front-end directors and the purpose of each one?

ESCON (EA) : for mainframe attachment and SRDF family links
FICON (EF) : provides the industry’s highest performance connectivity Option for the mainframe.
Fibre (FA/DA) : Connectivity option for open systems direct and SAN Attachment, and can be used for SRDF family remote Replication links.
iSCSI (SE) : Provides the industry’s first high-end Iscsi Implementation.
GigE (RE) : for SRDF family replication with compression support.

Explain Rule 17 in DMX?

Possible answers:
Rule of 17 ensured that FAs being used for host connectivity were in different power zones.

The rule of 17 is simply a way to make sure that the paths you connect your host to are not running on the same director, but one physically far away from it.

The original Rule of 17 was put into place to ensure that there was a path on each bus (odd and even).The bus architecture went away in DMX-1 ( Symm6). But we had 2 power zones; one zone for directors 1-8, and another zone for directors 9-16. So the Rule of 17 still had value.

but DIR 3 (odd) and DIR 4 (even) reside on different buses yet in the same power zone, so even if you had your host connected to 3 and 4 ..if that power zone went down ..Your hosts went down.

What are the Management Tools for DMX?

Symcli (Symmetrix Command Line Interface)
SMC (Symmetrix Management Console)
ECC (EMC Control Center)

What are the Enginuity Operational Layes?

Symmetrix Based Application
Host Based Symmetrix Application
Independent Software vendor application
EMC Solutions Enabler API
Symmetrix Enginuity Operating Environment Functions
Symmetrix Hardware

What are the major components of System Bay and Storage Bay in DMX?

System Bay Components:
Either six or eight disk directors and up to 12 channel directors (Combined total = 16).
From four to eight global memory directors.
Up to eight power supplies, each of having a dedicated Battery Back Up(BBU)
1U service processor with KVM (keyboard, video screen and mouse) and dedicated UPS.
Three cooling fan assemblies (each containing 3 fans).

Storage Bay Components:
120 or 240 disk drives per storage bay
Each Drive Enclosure (DE) includes:
Two link control cards (LCC).
Redundant power supplies with BBUs to provide standby power.
The DMX-4 storage bay has 2N power zones with independent power cables, each zone capable of powering the fully configured storage bay.
The storage bay can be populated with various combinations of currently available DMX one-inch low-profile 4 Gb/s Fibre Channel disk drives available in:
73 GB, 146 GB, 300 GB, and 400 GB Fibre Channel drives
73 GB and 146 GB Flash drives
500 GB and 1 TB SATA II disk drives

Can you explain about Read Hit, Read Miss and Fast Write and Delayed Write?

Read Hit: In a read hit operation, the requested data resides in global memory. The channel director transfers the requested data through the channel interface to the host and updates the global memory directory. Since the data is in global memory, there are no mechanical delays due to seek and latency.

Read Miss: In a read miss operation, the requested data is not in global memory and must be retrieved from a disk device. While the channel director creates space in the global memory, the disk director reads the data from the disk device. The disk director stores the data in global memory and updates the directory table. The channel director then reconnects with the host and transfers the data. because the data is not in global memory, the symmetrix system must search for data on the disk and then transfer it to the channel adding seek and latency times to the operation.

Fast Write A fast write occurs when the percentage of modified data in global memory is less than the fast write threshold. On a host write command, the channel director places the incoming blocks directly into global memory. For fast write operations, the channel director stores the data in global memory and sends a “channel end” and “device end” to the host computer. The disk director then asynchronously destages the data from global memory to the disk device.

Delayed Fast Write: A delayed fast write occurs only when the fast write threshold has been exceeded. That is the percentage of global memory containing modified data is higher than the fast write threshold. If this situation occurs, the symmetrix system disconnects the channel directors from the channels. The disk director then de-stages the data to disk. When sufficient global memory space is available. The channel directors reconnect to their channels and process the fast I/O requires as a fast write. The symmectrix system continues to process read operations during delayed fast writes with sufficient global memory present, this type of global memory operation rarely occurs.

How do you calculate number of cylinders for 120 GB LUN?

Maximum device sizes by Enginuity version
Enginuity version:__________:MBs:_______:CYLs:______:GBs
Enginuity 5874:_____________:245760:____:262668:____:240
Enginuity 5773 and earlier:_:61425:_____:65520:_____:59

Since DMX-4 supports maximum of 60GB hyper size, we have to create two hypers and form a Meta devices as 120GB LUN.
To calculate cylinders for 60GB LUN use the below formula
Cylinders = 60GB/15 tracks* 8 sectors* 16 blocks * 512 bytes
Cylinders = 60000000000/15*8*16*512
Cylinders = 60000000000/983040
Cylinders = 61035 cyl

To calculate the number of cylinders (for pre-Symmetrix DMX), use either of the following: blocks ÷ 960 or (size in megabytes) x 2.1333

To calculate the number of cylinders (for Symmetrix DMX and Symmetrix V-Max arrays), use the following: 1 cylinder = 15 tracks; each track is 64 KB, 15 x 64 tracks = .937 MB for each cylinder

What is the maximum hyper size in DMX-4?

Maximum Cylinders = 65520
Maximum Capacity = 59GB or 61425 MB

How many hypers can create in a Single disk in DMX4?

255 hypers per disk.

How many members can contain in one Meta?

1 Meta head + 255 members

How many LUN IDs available per FA port?

256 LUN IDs are available per FA port, 255 LUN IDs are usable out of 256.

What is Dynamic LUN addressing?

This feature will automatically selects and assigns the LUN IDs to the devices while device mapping to the port Instead of manually assigning address to the device while mapping

How do you add a new member to the existing Meta?

add dev XXXX to meta XXXX, protect_data=TRUE, bcv_meta_head=XXXX;

or for multiple ranges:
add dev XXX1:XXX6 to meta XXXX, protect_data=TRUE, bcv_meta_head=XXXX;

What is stripping and what is Concatenating?

Stripped Meta Devices:
Meta device addressing by striping divides each Meta member device into a series of stripes, addressing a stripe from each device before advancing to the next stripe on the first device. When writing to a striped volume, equal size stripes of data from each participating drive are written alternately to each member of the set.

Concatenated Meta Devices:
Concatenated devices are volume sets that are organized with the first byte of data at the beginning of the first device. Addressing continues to the end of the first device before any data on the next device is referenced. When writing to a concatenated device, the first meta device member receives all the data until it is full, and then data is directed to the next member and so on

What are the DMX-4 supported disk types, no. of disks and maximum capacity?

FC drives, iSCSI drives and Flash drives
15 drives per DAE
120 drivers per Cage
240 drives per Storage Bay
2400 drives per array If total of 10 storage bays connected
Maximum storage capacity is 1 PB.

Briefly explain the DMX-4 supported Device types?

Standard Devices: A Symmetrix device configured for normal Symmetrix operation under a desired protection method (such as RAID-1,RAID-S, and SRDF®).

Gatekeeper Devices: SCSI commands executed by SYMAPI are transferred to the Symmetrix array via a Symmetrix device that is designated as a Gatekeeper device. The gatekeeper allows you to retrieve configuration and status information from the Symmetrix array without interfering with normal device I/O operations.

Meta Devices: Allow individual devices to be concatenated to create larger devices.

BCV Devices: Specialized devices used to create a local copy of data contained in a standard Symmetrix device, which can be used for backup, restore, decision support, and application testing.

SRDF Devices (R1, R2 and R21) Devices configured as RDF1 or RDF2 to support SRDF operations.
R1 is source device for SRDF operations
R2 is target device for SRDF operations
R21 is used for multi hop SRDF operations

Virtual Devices: A host-accessible device containing track-level location information (pointers), which indicates where the copy session data is located in the physical storage. Device copies use virtual devices to support TimeFinder/Snap operations. Virtual devices consume minimal physical disk storage, as they store only the address pointers to the data stored on the source device or a pool of save devices.,

Save Devices: Special devices (not mapped to the host) that provide physical storage space for pre-update images or changed tracks during a virtual copy session of TimeFinder/Snap operations.

Device Masking (VCM)Devices: Symmetrix devices that have been masked for visibility to certain hosts. The device masking database (VCMDB) holds device masking records and typically resides on a 24 or 48 cylinder disk device..

DRV Devices: A non-user-addressable Symmetrix device used by the Symmetrix Optimizer to temporarily hold user data while reorganization of the devices is being executed. Typically, it is used by the Optimizer in logical volume swapping operations.

What is Vault drives and Hot Spare?

Vault Drivers: At the time of emergency shutdown of an Array, what ever the data in cache memory will be destaged/saved on temporary drives called vault drives

Hot Spare: At the time of physical drive failure hot spare drives will take place

What is Preview, Prepare and Commit while using Symconfigure command?

The preview argument verifies the syntax and correctness of each individual change defined, and then terminates the session without change execution.

The prepare argument performs the preview checks and also verifies the appropriateness of the resulting configuration definition against the current state of the Symmetrix array; the argument then terminates the session without change execution

The commit argument completes all stages and executes the changes in the specified Symmetrix array

What are the possible device service states and device status states?

Device Service States : Normal, Failed and Degraded
Device Status States : Ready, Not Ready and Write Disable.

How do you reserve the devices?

symconfigure -sid XXXX -f createdev.cmd -expire expiration date-owner myself -comment "this devices are reserved for SRDF activity" reserve

How do you create the Disk Groups

We can not create Disk Groups, It should be done by changing BIN file by CE.
We can rename the existing disk groups.
Example: symconfigure -sid 207 -cmd “set disk_group 4 disk_group_name = flash_dsks;” -v -nop commit

How do you check the free space by Disk group and Array as whole?

By Disk Group : Symdisk -sid XXXX list -by_diskgroup
Array as whole : Symconfigure -sid XXXX list -freespace

How do you check the total assigned devices to a particular Host?

Symmaskdb -sid XXXX list devs -wwn "host hba wwn"

How do you check the total allocated storage of a particular Host?

symmaskdb -sid XXXX list capacity -Host hostname

What is pre check list to assign storage to the host?

Verify the available free space in the symmetrix array
symconfigure -sid SymmID [-v | -freespace [-units cylinders | MB]] list
symdisk -sid "SymID" list -disk_group "GroupNumber"

Verify the Symmetrix status
Symconfigure -sid "SymID" verify

If any hung activities found abort
symconfigure -sid "SymID" abort

Explain step by step procedure to provide storage to the Host?

1. Creating STD device
2. Meta Device Creation
3. Mapping
4. Masking

Example:
Create a commandfile with the following entry to create hypers.
Create dev count=8, size=12394, emulation=FBA, config=2-way-mir, disk_group=2;

Execute the command file using symconfigure command with preview, prepare and commit options.
Symconfigure -sid "SymID" -f Commandfile.cmd -v -noprompt commit

Verify the newly created devices
symdev -sid "SymID" list -noport

Create a commandfile with following entry to form metas and devices to the meta head.
Form meta from dev 26CA, config=striped, stripe_size=1920;
add dev 26CB:26E4 to meta 26ca;

Execute the command file using symconfigure command with preview, prepare and commit options.
symconfigure -sid "SymID" -f Commandfile.txt -v -noprompt commit

Verify the newly created meta devices
symdev -sid "SymID" list -noport

Find the host connected Director and Port details
symcfg -sid 4282 list -connections

Find the available addresses on that port
symcfg -sid "SymID" list -address -available -dir 7d -p 0

Create a commandfile with the following entry to map the device to the FA port
map dev 26ca to dir 7d:0, lun=036;

Execute the commandfile using symconfigure with the preview, prepare and commit options.
Symconfigure -sid 4282 -f Commandfile.txt -v -noprompt commit

Mask the devices to the host HBA and refresh the sym configuration
symmaskdb -sid "SymID" -wwn 10000000c93f62cf -dir 7d -p 0 add devs 26ca -nop
Symmask -sid "SymiD" -refresh

Rescan the disks and refresh the powerpath or reboot the server to get the assigned devices at host-end

How do you check particular device geometry?

symdev -sid XXXX show dev 002C

How do you check the particular device is connected to which Host?

symmaskdb -sid XXXX list assignment -dev 002c

What are the steps for storage reclamation?

Unmasking
Write Disable
Un-mapping
Dissolve meta
Deleting hypers

1. Unmasking devices from the host
symmaskdb -sid 4282 -wwn 10000000c93f62cf -dir 7d -p 0 remove devs 26ca

2. Refresh the Symmetrix Array
Symmask -sid 4282 -refresh

3. Write Disable the devices before unmapping from the Director port
symdev -sid 4282 write_disable 26ca -sa 7d -p 0 -noprompt

4. Create a cmd/txt file
Unmap dev 26ca from dir all:all;

5. Perform preview operation using symconfigure command
Symconfigure -sid 4282 -f unmap.txt -v -nop preview

6. Perform prepare operation using symconfigure command
Symconfigure -sid 4282 -f unmap.txt -v -nop prepare

7. Perform Commit operation using symconfigure command
Symconfigure -sid 4282 -f unmap.txt -v -nop commit

8. Verify that the device has been unmapped
Symdev -sid 4282 list -noport

9. To Dissolve meta, create a cmd/txt file
Dissolve meta dev 26ca;

10. Perform preview operation using symconfigure command
Symconfigure -sid 4282 -f dissolve.txt -v -nop preview

11. Perform prepare operation using symconfigure command
Symconfigure -sid 4282 -f dissolve.txt -v -nop prepare

12. Perform Commit operation using symconfigure command
Symconfigure -sid 4282 -f dissolve.txt -v -nop commit

13. Verify that the meta has been Dissoved.
Symdev -sid 4282 list -noport

14. To delete the hypers create a cmd/txt file.
Delete dev 26ca;

15. Perform preview operation using symconfigure command
Symconfigure -sid 4282 -f dissolve.txt -v -nop preview

16. Perform prepare operation using symconfigure command
Symconfigure -sid 4282 -f dissolve.txt -v -nop prepare

17. Perform Commit operation using symconfigure command
Symconfigure -sid 4282 -f dissolve.txt -v -nop commit

18. Verify that Hypers have been deleted.
Symdev -sid 4282 list -noport

How many mirror positions RAID-1 and RAID-5 will occupy?

RAID-1 occupies 2 mirror positions
RAID-5 occupies 2 mirror positions

How do you convert the concatenating meta device to stripped meta?

convert meta XXXX, config=striped, stripe_size=1920, protect_data=TRUE, bcv_meta_head=XXXX;

Host is unable to see the storage, how do you troubleshoot?

Check that the host is logged in to the Array
Check that the cable connectivity status by logging in to the host
Check that the HBA drivers are properly configured
Check the Zoning table by logging in to the switch
Check that the devices status in Array
Check the VCMDB for masking information, etc..

What is Thin Provisioning?

Thin provisioning is a method of optimizing the efficiency with which the available space is utilized in storage area networks. Thin provisioning operates by allocating disk space in a flexible manner among multiple users, based on the minimum space required by each user at any given time.

How do you create thin pools and thin devices?

Creating Thin Pools
Creating Data devs and added these Data devs to Thin Pools
Creating TDEVs and bind these TDEVs to Thin Pool
Assign TDEVs to host.

Explain step by step procedure to setup new host?

Let us assume cable connectivity is done properly
Install HBA drivers in host.
Install Power path if required.
Check that the HBA ports are showing online
Create zoning at switch end.
Check that this host is logged in to the Storage array
Create LUN/hypers in storage array
Form meta devices if required
Map the devices to the FA port.
Mask the devices to the host hba (wwn).
Refresh the Array to affect the changes.

How do you check the failed components in Symmetrix Array?

Symcfg -sid 150 list -env_data -service_state failed

How do you check the failed disks in the Symmetrix Array?

Symdisk -sid XXXX list -failed

What is the purpose of Gate Keeper device?

Low-level I/O commands executed using SYMCLI are routed to the Symmetrix array by a Symmetrix storage device that is specified as a gatekeeper.
The gatekeeper device allows SYMCLI commands to retrieve configuration and status information from the Symmetrix array without interfering with normal Symmetrix operations.
The gatekeeper must be accessible from the host where the commands are being executed.

How many gate keeper devices are required per Array?

It depends on the Symmetrix management applications using in management servers,
As per EMC recommendations 6 gatekeepers are required per management host using symcli

How to list hosts and their EMC registered software, using Solutions Enabler?

Symcfg -sid XXXX list -applications

What is VCMDB and how do you take the backup?

The device masking database (VCMDB) holds device masking records and typically resides on a 24 or 48 cylinder disk device..
Symmaskdb -sid XXXX backup -f filename

How do you list the Hosts which are connected to particular director port?

Symmaskdb -sid XXXX list database -dir XX -p X

How do you check the number of storage bays connected to the system bay and number of disks in each storage bay?

Symcfg -sid XXXX list -env_data

How do check the devices which are not mapped and masked?

Symdev -sid 4282 list dev -noport

How do you check the devices which are mapped to FA but not masked to any host?

Symmaskdb -sid 123 list no_assignment -dir ALL -p ALL

How do you check the login hosts in the Symmetrix Array?

Symmask -sid 4282 list logins

How to display and set the Symmetrix metrics?

Symcfg -sid XXXX -SA all list -v
Set Symmetrix MatricName=MatricValue

How do you check the configured environmental variables?

Symcli -def

Can windows, Linux, Solaris share the same FA in DMX?

Yes, if they share the same port flags

What are the Symmetrix External locks and how to check and release?

Symmetrix external locks are used by SYMAPI (locks 0 to 15) and also for applications assigned by EMC (>15) to lock access to the entire Symmetrix arrayduring critical operations

We can check the external locks by giving the below command
symcfg -sid XXXX list -lockn

We can check the external locks by giving the below command
symcfg release -sid -lockn 15 -force

How to monitor performance of EMC Symmetrix?

Using Performance Monitoring feature in EMC Control Center
Using SYMSTAT symcli command

How do you check the cache activity of front-end directory?

symstat -sid 4282 -type cache -i 5 -c 4 -sa all

How do you check the I/O requests and throughput of selected disk?

Symstat -sid 4282 -type disk -i 5 -c 3 -disk 2a,C,5

What are the available performance types in SYMSTAT command?

REQUESTS: Reports I/O requests and throughput for selected devices, directors, or SRDF/A sessions. (This is the default type; if no type is specified REQUESTS is used.)
BACKEND: Reports back-end I/O requests and throughput for selected devices.
PORT: Reports performance statistics for a director port. ISCSI Report Gig-E network statistics.
CACHE: Reports cache activity for selected front-end or remote link directors, or SRDF/A sessions.
MEMIO: Reports cache memory to disk activity for selected devices. PATH Report R-Copy path information for nonincremental sessions. Symmetrix arrays that have all or some incremental sessions will report an error.
CYCLE: Report cycle summary information for SRDF-A sessions.
DISK: Reports back-end I/O requests and throughput for selected disks.
PREFETCH: Reports track prefetch disk activity for selected back-end directors only.DMSP Reports dynamic mirroring service policy (DMSP) statistics for the selected device(s).
RDF: Reports SRDF statistics from the perspective of RA groups, devices, or directors.

What is symmetrix optimizer and how it works?

Symmetrix Optimizer improves array performance by continuously monitoring access patterns and migrating devices (Symmetrix logical volumes) to achieve balance across the disks in the array
Step 1: Symmetrix Optimizer builds a database of device activity statistics on the Symmetrix back-end.

Step 2: Using the statistical data collected, configuration information, and the user-defined parameters, the Optimizer algorithm identifies busy and idle devicesand their locations on the physical drives. The algorithm tries to minimize average disk service time by balancing I/O activity across physical disks. Optimizer determines which disks require balancing by locating busy devices close to each other on the same disk, and/or by locating busy devices on faster disks or faster areas of the disks. Optimizer takes into account the speed of the disk, the disk geometry, and the actuator speed to determine faster disks.

Step 3: Once a solution for load balancing has been developed, the next phase is to carry out the Symmetrix device swaps. This is done using established TimeFinder technology, which maintains data protection and availability. we can specify whether swaps should occur in a completely automated fashion, or if the device swaps require user approval before the action is taken.

Step 4: Once a swap function completes, Symmetrix Optimizer continues data analysis for the next swap.

What is Symmetrix QoS and how it works?

Quality of Service (QoS) allows more flexibility in managing Symmetrix system’s performance. By increasing the response time for specific copy operations on selected devices, we can increase the overall performance of the other Symmetrix devices.

The QoS (Quality of Service) feature allows us to adjust the data transfer pace on specified devices, or devices in a device group, for certain operations.

The contention for cache access can be quality of service managed by the least recently used (LRU) ring partitions in the Symmetrix cache.

We can control the priority service time of devices and control cache partitions for different device groupings.

What is the purpose of Symmetrix Change Tracker?

To measure changes to data on a Symmetrix volume or group of volumes.
Change Tracker data is often used to analyze and design TimeFinder and Symmetrix Remote Data Facility (SRDF) configurations.
Change Tracker (DeltaMark) session must be created using the symchg create command. The symchg mark command is then used to perform a timestamp and mark the selected area of disk storage occupied by a data object using a DeltaMark bitmap

What is Dynamic Cache Partitioning?

A QoS feature, dynamic cache partitioning allows the Administrator the means to dynamically control the cache area size, servicing a given device group I/O, by defining flexible partitions through cache memory.

Dynamic Cache Partitioning divides the cache memory into multiple partitions with unique names and their device path assignments.

Partition areas can be made static or dynamic in size. The dynamic partitioning provides flexibility to the amount of floating memory that can be allocated with a high and low watermark. This allows memory resources to be temporarily donated to other partitions when needed.

The symqos command allows you to create partitions for different device groupings in addition to the default partition that all devices belong to initially. Each partition will have a target cache percentage as well as a minimum and maximum percentage. In addition, you can donate unused cache to other partitions after a specified donation time.

What are the logs available at host-end and on symmetrix array?

Host-end logs are available in \Symapi\log folder
Event logs and Audit logs in symmetrix array

How do you monitor the real time events on symmetrix array with example?

To monitor real time 100 event records with 600 seconds interval in the symmetrix array
Symevent -sid 4282 monitor -i 600 -c 100 -warn/-error/-fatal

How do you track the history of events on symmetrix array with example?

To list all events in symmetrix array
Symevent -sid 4282 list

To list specific period of time events in event logs
Symevent -sid 4282 list -v -start 9:00 -end 17:00

How do you check the audit logs on symmetrix array?

To show the details about audit log it self.
Symaudit -sid 4282 show

To list the audit log records of specific period of time.
Symaudit -sid 4282 list -v -start_time 7/11:9:00 -end_time 7/11:10:00

To monitor the real time audit logs 100 records with 30sec interval.
symaudit -sid 4282 monitor -i 30 -c 100

What is Symmetrix ACL?

To create access control list on symmetrix array to implement host level or user level security.

Explain step by step to setup the access controls on symmetrix array?

Create Access Group:
(Create a command file with the following entries)
Create accgroup AccessGroupName;
(Execute the command file)
Symacl -sid 4282 commit -file commandfile

Add host access ID or user access ID to access group:
(Create a command file with the following entries)
Add host accid Id name Idname to accgroup GroupName;
Add user accid Id name Idname to accgroup GroupName;
(Execute the command file)
Symacl -sid 4282 -file "CommandFileName" commit

Create Access Pools:
(Create a command file with the following entries)
Create accpool AccessPoolName;
(Execute the command file)
Symacl -sid 4282 commit -file "commandfile"

Add devices to the access pool
(Create a command file with the following entries)
Add dev StartDevName:EndDevName to accpool AccessPoolName;
(Execute the command file)
Symacl -sid 4282 commit -file "commandfile"

Grant Rights to Access Groups:
(Create a command file with the following entries)
Grant access=Base/BCV/RDF to accgroup AccessGroupName to accpool AccessPoolName;
(Execute the command file)
Symacl -sid 4282 commit -file "commandfile"

How do you take the backup/restore of ACLs?

Symacl -sid 4282 backup -file "commandfile"
Symacl -sid 4282 commit -restore -f commandfile

What is Symmetrix User Authorization?

Set up or update the Symmetrix array user authorization information

Explain step by step procedure to setup user authorization on symmetrix array?

User-to-role mappings have to be created:
(Create a command file with the following entry (ex:rolemap.txt))
Assign user H:Host\username to role Monitor;
Assign user D:Eng\username to role Admin;
(Execute the above file)
Symauth -sid 4282 -f rolemap.txt commit.
(Roles: None, Monitor, Storage admin, admin, Auditor, SecurityAdmin)

Enable the user authorization:
Symauth -sid 4282 enable

How do you perform backup and restore user authorization information?

Symauth -sid 4282 backup -f backupfile.cmd commit
Symauth -sid 4282 restore -f backupfile.cmd commit

What is the purpose of bin file in SYMAPI database?

It is a database file in the host which stores the symmetrix array’s configuration data. Can be used to get the configuration data offline.

How do you prepare the Storage Capacity planning reports by host wise?

1. By using EMC Control Center
2. By using symcli commands symcfg and symdisk
Symcfg -sid 4282 list -connections -capacity
Copy and past the output of the above command in excel file and format according to the requirement.
Or
Symdisk -sid 4282 list -by_diskgroup
Copy and past the output of the above command in excel file and do the format according to the requirement.

By using what symcli command we can check the HBA details?

Syminq hba -fibre

SRDF - Possible Questions for Interview

What is Business Continuity?

Business Continuity is the preparation for, response to, and recovery from an application outage that adversely affects business operations.

What are the Business Continuity tools available for symmetrix?

Power path at host end TimeFinder/Mirror, Clone and Snapshot for local replication SRDF for remote replication.

Business Continuity addresses what?

Business Continuity Solutions addresses systems unavailability, degraded application performance, or unacceptable recovery strategies.

What is RPO and RTO?

RPO refers to the maximum amount of data loss an application can tolerate as measured in time. In other words, the amount of data loss that can be tolerated (cost of transaction versus risk).

RTO refers to the maximum time a company budgets to bring an application back online in the event of a disaster. In other words, the time it takes to recover the data once a disaster or other recovery event is declared (risk versus cost)

What are the different types of Device Groups?

Regular, RDF1, RDF2 and Composite group

Briefly explain baout Regular, RDF1 and RDF2 device groups?

Regular device groups are normally used for TimeFinder operations
RDF1 and RDF2 device groups are normally used for SRDF operatins

What is composit group?

A composite group is a user-defined group of device members that can span multiple Symmetrix arrays and SRDF groups. The CG type may be defined as REGULAR,RDF1, RDF2, or RDF21, and may contain various device lists for standard, BCV, virtual (VDEV), RBCV, BRBCV, second hop standard, and second hop BCV.

What is the difference between TimeFinder and SRDF?

Time Finder is for local replication operations
SRDF is for remote replication operations

What are the different types of Remote Link directors used for SRDF?

RF (Fibre Channel directors)
RA (ESCON directors)
MPCD (Multiprotocol Channel Directors) available with these channel connections
FICON
iSCSI for host
GigE (RE) for SRDF

How many dynamic RDF groups can be created in an array?

Symmetrix DMX supports up to 64 total RDF groups.

What are the different types of Link configurations for SRDF?

Unidirectional: If all primary (source or R1) volumes reside in one Array and all secondary (target or R2) volumes reside in another Array, write operations move in one direction, from primary to secondary. Data moves in the same direction over every link in the SRDF group.
Bidirectional: If an SRDF group contains both primary and secondary volumes, write operations move data in both directions over the SRDF links for that group.
Dual-Directional: With a dual-directional configuration, multiple SRDF groups are used; some groups send data in one direction, while other groups send data in the opposite

How the SRDF synchronous mode of operation works?

Write I/O received from host/server at the source
The I/O is transmitted to the target
An acknowledgment is provided by target back to the source
The I/O is serviced to the host

How the SRDF semi synchronous mode of operation works?

An I/O write is received from the host/server at the source.
The I/O is serviced to the host/server.
The I/O is transmitted to the cache of the target.
An acknowledgment is provided by the target back to the source.

How the SRDF Adaptive copy mode of operations works?

Write I/O received from host/server at the source
The I/O is serviced to the host I/O accumulates in/onSymmetrix cache in Write Pending Mode R1 volumes in Disk Mode.
I/O is transmitted to the target.
An acknowledgment is provided by target back to the source.

What is Writing Pending and Disk Mode of Adaptive Copy?

I/O is accumulates in Symmetrix cache in Write Pending Mode
I/O is accumulates in R1 volume in Disk Mode

What is the purpose of Adaptive copy mode?

Adaptive Copy Mode is used primarily for data migrations and data center moves.

How the SRDF Asynchronous mode of operation works?

Write I/O received from host/server at the source
The I/O accumulates in Source Symmetrix cache
The I/O is serviced to the host
The I/O is continually transmitted to the target
The I/O accumulates in Target Symmetrix cache

What is SRDF Domino mode?

Domino Mode is used in conjunction with other SRDF modes except SRDF/A. It effectively stop all write operations to both source and target volumes if target volume become unavailable, or if all SRDF links become unavailable. User will need to manually re-enable the source volumes. While such a shutdown temporarily halts production processing, domino modes can prevent data integrity exposure that causes the inconsistent image on the target volume.

How the SRDF domino mode works?

Write I/O received from host/server at the source
The I/O fails to transmit to the target
Both Source and Target become unavailable

How many R2 devices can be paired with one R1 device concurrently?

Two

What are the restrictions of SRDF device group?

All devices in a disk group must be in the same Symmetrix ICDA
All devices must be of the same type (RDF1, RDF2, Regular)
A device can only belong to a single Device Group per SYMAPI database

How do you check the connectivity status of SRDF link?

Symrdf –sid "SymID" ping
Symrdf –sid "SymID" -RA list all

What are the disaster recovery operations?

Failover: from the source side to the target side, switching data processing to the target side.
Failback: from the target side to the source side by switching data processing to the source side.
Update: the source side after a failover while the target side may still be operational to its local host.

How will failover operation works?

Write Disable device(s) on SA at source (R1)
Suspend RDF link(s)
Read/Write Enable device(s) on RA at target (R2)

How will update operation works?

Suspend RDF link(s)
Merge device track tables between source and target
Resume RDF link(s)

How will failback operation works?

Write Disable device(s) on RA at target (R2)
Suspend RDF link(s)
Merge device track tables between source and target
Resume RDF link(s)
Read/Write Enable device(s) on SA at source (R1)

What are the decision support SRDF operations?

Establish:
Resume Normal SRDF operations
Preserves data on the source (R1) volumes, discarding changes to the target (R2) volumes

Split:
Suspends link between source (R1) and target (R2) volumes
Enables read and write operations on both source and target volumes

Restore
Resume SRDF operations
Preserves data on the target (R2) volumes, discarding changes to the source (R1) volumes

How the split operation will works?

Suspend RDF link(s)
Read/Write Enable device(s) on RA at target (R2) also.

How will establish operation works?

Write Disable device(s) on RA at target (R2)
Suspend RDF link(s)
Resume RDF link(s)
Merge device track tables between source and target
Resume RDF link(s

How will restore operation works?

Write Disable device(s) on SA at source (R1)
Write Disable device(s) on RA at target (R2)
Suspend RDF link(s)
Merge device track tables between source and target
Resume RDF link(s)
Read/Write Enable device(s) on SA at source (R1)

Can you briefly explain about SRDF/S?

SRDF/S is a configuration of multiple Symmetrix units that maintains real time copies of logical volume data in more than one location.
Facility for maintaining real-time or near-real-time physically separate mirrors of selected volumes.
Uses no host CPU resources – Mirroring done at the storage level
Operating system independent
There is a performance impact on arrays
Limited distance

Can you briefly explain about SRDF/Asynchronous?

The Symmetrix array provides a consistent point-in-time image on the target (R2) device, which is a short period of time behind the source (R1) device. Managed in sessions, SRDF/A transfers data in predefined timed cycles or delta sets to ensure that data at the remote (R2) site is dependent write consistent.
SRDF/A provides a long-distance replication solution with minimal impact onperformance that particularly preserves data consistency with the database.
Promotes efficient link utilization resulting in lower link bandwidth.
Maintains a dependent write consistent copy on the R2 devices at all times.
Supports all current SRDF topologies, including point-to-point and switched fabric.
Requires no additional hardware, such as switches or routers.
Supports all hosts and data emulation types supported by the Symmetrix array
Minimizes the impact imposed on the back-end DA directors.
Provides a performance response time equivalent to writing to local non-SRDF devices.
Allows restore, failover, and failback capability between the R1 and the R2 sites.

What are the factors that effects the SRDF/A implementation?

SRDF link Bandwidth, Symmetrix Cache and Workload.

What is SRDF Automated Replication?

SRDF/AR allows users to automate the sequence of SRDF and TimeFinder mirror operations. The automated sequence, cycle, is performed on a user-defined interval called cycle time. it is usually set to operate in Adaptive Copy mode due to the long distance between local and remote sites. This allows the users to save on network bandwidth thus minimizing the network costs without compromising the integrity of the data.
Allows business restart site to be at any distance away from source
Collaboration of SRDF and TimeFinder commands
Minimizes network costs

How do you change or set the SRDF mode of operations?

Examples:
symrdf -g "DgName" set mode sync
symrdf -cg set mode semi
symrdf -f FileName set mode async
symrdf -g "DgName" set domino on
symrdf -g "DgName" set domino off
symrdf -g "DgName" set mode acp_wp
symrdf -g "DgName" set mode acp_off
symrdf -g prod set mode acp_disk
symrdf -g prod set mode acp_off

What is the background process during the SRDF pairs full establish?

The target (R2) device is Write Disabled to its local host I/O.
Traffic is suspend on the SRDF links.
All the tracks on the target (R2) device are marked invalid.
All tracks on the R2 side are refreshed by the R1 source side. The track tables are merged between the R1 and R2 side.
Traffic is resumed on the SRDF links.

What is the background process during the failback?

The target (R2) device is Write Disabled to its local hosts.
Traffic is suspended on the SRDF links.
If the target side is operational, and there are invalid remote (R2) tracks on the source side (and the force option is specified), the invalid R1 source tracks are marked to refresh from the target side.
The invalid tracks on the source (R1) side are refreshed from the target R2 side. The track tables are merged between the R1 and R2 sides.
Traffic is resumed on the SRDF links.
The source (R1) device is Read/Write Enabled to its local hosts

How will the SRDF restore operation works?

The source (R1) device is Write Disabled to its local hosts.
The target (R2) device is Write Disabled to its local hosts.
Traffic is suspended on the SRDF links.
All tracks on the source (R1) device are marked as invalid.
All R1 tracks are refreshed from the R2 side. The track tables are merged between the R1 and R2 side.
Traffic is resumed on the SRDF links.
The source (R1) device is read/write enabled to its local hosts.

Explain step by step procedure to perform SRDF/S?

SRDF/S normal operations
Creating device groups in source and target Arrays:
symdg -type RDF1 create "SourceDgName"
symdg -type RDF2 create "TargetDgName"

Adding devices R1 and R2 devices to source and target device groups
symld -g "SourceDgName" add dev "SymDevName"
symld -g "TargetDgName" add dev "SymDevName"

Setting SRDF mode of operation:
symrdf -g "DgName" set mode sync

SRDF normal operations:
symrdf -g "DgName" suspend
symrdf -g "DgName" resume

SRDF/S disaster recover operations
symrdf -g "DgName" failover
symrdf -g "DgName" update -remote
symrdf -g "DgName" failback

SRDF/S decission support operations:
symrdf -g "DgName" split
symrdf -g "DgName" restore
symrdf -g "DgName" establish

Explain step by step procedure to perform SRDF/Asynchronous?

Creating RDF group:
symrdf addgrp -label -rdfg "GrpNum" -sid "SymID" -dir "DirNum" -remote_sid –remote_dir -remote_rdfg "RemoteRdfgNum"

Create device pair:
symrdf -file "DevFileName" -sid "SymID" -rdfg "GrpNum" -type r1 -establish -g "DgName" createpair –noprompt

Changing SRDF mode :
symrdf -g "DgName" set mode async -noprompt

Explain step by step procedure to perform SRDF/AR for single hop?

Create a device group:
symdg create "DgName" -type regular

Add the standard device to the device group:
symld -g "DgName" add dev "SymDev"

Associate the R1/BCV device:
symbcv -g "DgName" associate dev "SymBcvDev"

Associate the remote BCV device:
symbcv -g "DgName" associate dev -rdf -bcv

Prepare the mirror states and start the session:
symreplicate -g "DgName" start -option "Path" -setup -consistent

Stop the session:
symreplicate -g "DgName" stop -nop

Restart the session:
symreplicate -g "DgName" restart -nop

OR

Create a device group:
symdg create "DgName" -type regular

Add the standard device to the device group:
symld -g "DgName" add dev "SymDev"

Associate the R1/BCV device:
symbcv -g "DgName" associate dev "SymBcvDev"

Associate the remote BCV device:
symbcv -g "DgName" associate dev "SymBcvDev" -rdf -bcv

Establish the STD and R1/BCV:
symmir -g "DgName" establish -full

Split the STD and R1/BCV:
symmir -g "DgName" split -consistent

Resume SRDF link:
symrdf -g "DgName" resume -bc

Establish the R2 and remote BCV:
symmir -g "DgName" est -full -rdf -bcv

Split the R2 and remote BCV:
symmir -g "DgName" split -full -rdf -bcv

Establish the STD and R1/ BCV:
symmir -g "DgName" establish

How the symstar will be configured?

Uses concurrent and cascaded SRDF/Synchronous and SRDF/Asynchronous links to replicate source data synchronously to a nearby regional site and asynchronously to a distant remote site.

How do you recover suspended or partitioned state session?

Using symrecover command.

What are the access rights required if ACLs enabled?

BASE and CFGSYM access rights required.

Can we migrate the R1 data to larger R2 device?

Yes, we can migrate the R1 data to larger R2 but we can not perform device swap, SRDF/Star operations, we can not restore back to the R1 device and Concatenated meta devices are not supported.

How do you create groups for dynamic RDF pairs in a device file?

Creating dynamic pairs in a device file:
symrdf createpair -file "DevFileName" -sid 55 -rdfg 2 -type rdf1 -invalidate r2 -g "DgName"

What is dynamic R1/R2 swap?

The dynamic R1/R2 swap feature swaps the SRDF personality of the SRDF device designations of a specified device or composite group

What is link limbo and how do you specify?

feature allows you to set a specific length of time for Enginuity to wait when a down link is detected before updating the link status. If the link status is still Not Ready after the link limbo time expires, devices are marked Not Ready to the link.
symrdf -sid 80 -rdfg 4 set link_limbo 60

How do you create/add the dynamic SRDF group?

symrdf addgrp -label "RdfGrpName" -rdfg "RdfGrpNum" -sid "SymID" -dir "DirNum" -remote_rdfg 4 -remote_sid "SymID" -remote_dir "RemDirNum"

How do you add dynamic SRDF pairs to dynamic SRDF group?

symrdf createpair -file "DevFileName" -sid "SymID" -rdfg "RdfGrpNum" -type rdf1 -invalidate r2

What are the Symmetrix Array-wide parameter in SRDF/A?

Maximum SRDF/A Cache Usage and Maximum Host Throttle Time

How do you set the metrics on symmetrix for SRDF/A?

set symmetrix rdfa_cache_percent = 94;
set symmetrix rdfa_host_throttle_time = 0;

What is RDF group session priority parameter?

When SRDF/A needs ts drop sessions when the cache WP limit is reached, the sessions will be dropped starting with priority values of 64 with a setting of 1 being the last to be dropped.

What is the SRDF mode of operation for SRDF/AR?

Adaptive copy mode.

What are the required options for symreplicate options file?

SYMCLI_REPLICATE_HOP_TYPE and one of SYMCLI_REPLICATE_CYCLE or SYMCLI_REPLICATE_CYCLE_DELAY

What is consitency and how to enable?

Consistent split allows us to avoid inconsistencies and restart problems that can occur if you split a database-related BCV without first quiescing the database.
symrdf -g enable

What is automatic tripping and manually tripping of composite group?

Automatic Tripping - Occurs when one or more R1 source devices in an consistency enabled Composite Group cannot propagate data to their corresponding target devices.
Manual Tripping - Occurs when you invoke the symrdf –cg suspend or split command. 

Symmetrix TimeFinder - Possible Questions for Interview

What is the purpose of TimeFinder/ Mirror, Clone and SNAP?

TimeFinder/Mirror : Backups and Web content refresh
TimeFinder/Clone : Data warehousing and Application testing
TimeFinder/Snap : Local recovery and 1-hour RPO

What are all possible commands used for TimeFinder Operations (Mirror, Clone and Snapshot)?

Symmir is for timefinder mirror operations
Symclone is for timefinder clone operations
Symsnap is for timefinder snap operations
symconfigure is for devices creation
symdg is fir device group operations
symld is for performing operatoins on devices in a device group
symbcv is for performing operations on devices in a device group
symdev is for performing operations on devices
symcfg is for performing configuratoin related operations

What is the BCV device?

BCV is Business Continuance Volume
Can be dynamically and non-disruptively established and synchronized
Can be split instantly to create “point-in-time” copy.
Uses for the BCV copies can include backup, restore, decision support, and applications testing.

Explain step by step procedure for TimeFinder Mirror Operations?

Establish: Synchronize the standard volume to the BCV volume
Split: Terminate mirror relationship between standard and BCV volumes
Restore: Synchronize contents of BCV volume to the standard volume
Verify: Provide current status of BCV/standard volume relationship.

Creating regular device group
symdg create -type regular

Adding standard devices to the device group
symld -g add dev -sid XXXX

Associating BCV devices to the device group
symbcv -g addl dev -sid XXXX

Establish mirror relationship between STD and BCV devices
symmir -g -full establish -v

Verifying the synchronization status
symmir -g verify -synched

Splitting mirror relationship between STD and BCV devices
symmir -g split

Restoring BCV
symmir -g restore

Verify the restore status
symmir -g verify -synched

What is the status of Source and Target devices at the time of Establish, Split and Restore in mirror operations?

Establish: STD device have R/W access and BCV device is in NR state.
Split : Both STD and BCV will have R/W access
Restore : STD device have R/W access and BCV device is in NR state.

How will synchronization happen when perform establish?

The Symmetrix array checks that both the standard device and the BCV device are the same size, the device specified as the BCV has the BCV attribute, the standard device does not already have a BCV device assigned to it.
If the standard device is a meta head device, then the BCV must also share the same meta device properties. All meta members will be implicitly established along with the meta head device.
The BCV device is set as Not Ready to the host.
The BCV device is assigned as the next available mirror of the standard device.
The contents of the standard device are copied to the BCV.

What is the background process in split operation?

Command validity is checked. For example, the Symmetrix array makes sure that the standard device has an active BCV mirror and that the standard and BCV devices comprise a BCV pair.
I/O is suspended to the standard device until the split operation completes.
Any pending write transactions to the standard device and the BCV device are destaged.
The BCV device is split from the BCV pair.
The BCV device state is changed to Ready, enabling host access through its separate address (BCV001).

What is default option while performing establish?

Incremental is the default action for establish.

What is Power path Split?

Power Path holds I/O during split - Read and write I/O, executed from host doing I/O, affects only one host, does not require independent access to a gatekeeper.

What is ECA (Enginuity Consistent Assist) split?

Symmetrix holds I/O during split - Write I/O (subsequent reads after first write), Executed by any Symmetrix-attached host, multiple host support, requires independent access to a gatekeeper.

What are the precautions we have to take while performing establish?

Host access to BCV devices must be stopped.
Stop application, unmount file system, and deactivate volume group.

What are the precautions we have to take while restoring a mirror?

All access to the STD device must be stopped. Applications must be stopped, file systems must be unmounted, and volume groups must be deactivated when a restore is initiated. Since the host is having read and write access to the standard device, if any application is using the standard volume during a restore, the results would be unpredictable.

What is Protected BCV Establish?

Both M1 and M2 of standard device instantly synchronized with the M1 and M2 of 2-way mirror BCV.
In a 2-way BCV mirror configuration for a normal establish M2 is fixed and can only be updated from M1 after a split.

What is reverse split?

Data will be moved from the M2 mirror of the BCV to its M1 mirror.
During a reverse split, the fixed BCV mirror (M2) will refresh the moving mirror (M1) after the split operation. This is desirable when we need to revert to an older copy of the data that was on the BCV before it was established.

 What is Protected BCV Restore?

A protected restore feature allows the contents of a BCV to remain unchanged during and after a restore operation, even while the BCV and the standard are joined.
Restore a BCV to a STD but do not propagate STD writes to the BCV – Used to retain original BCV data after the restore process

How many BCVs can be supported in multi BCV functionality?

Eight BCVs

How many BCVs can be established concurrently to the standard volume?

Two BCVs

Is TimeFinder Mirror Supports concurrent restores?

Concurrent restores are not allowed.

Is the BCV can be mounted to the source host?

BCV mirror can be mounted to same host but there will duplicate disk signatures/volume IDs need to change.

One device can be a member of how many device groups?

Only one device group

Device Groups are host based or Array based?

Host based. If we enable the GNS in symmetrix array then we can create array wide device group.

What is foreground and background instant split?

Foreground split completes instantly and returns a success status to the production.
Background split continues to split the mirror until the split is complete. If the production server tries to access information on a track that has not been split,the system first splits the track and then completes the I/O request

Expbrlain Step by step procedure for TimeFinder Clone Operations?

Create: Create relationship between standard and Clone
Activate: Clone is now active and available immediately for read/write access – Production I/O is processed against standard
Re-Create: Clone is re-attached to Standard for new point-in-time copy (incremental/differential)
Establish: Create and activate
Restore: Re-attached to Standard and incremental or full restore is performed
Terminate: Terminate the relationship between source and target

symdg create -type regular
symld -g add -sid dev XXX1
symld -g add -sid dev XXX2
symclone -g create
symclone -g activate
symclone -g query
symclone -g terminate

What are the different options with clone create and Explain?

CopyOnAccess: Only modified tracks are copied to clone volume after activation
Full Device Copy: Full copy in the background starts after activation
Precopy: Full copy in the background starts after creation
Differential: Used with Full Copy or Precopy (implied Full Copy by default) – Required if recreate clone session is planned – Required if incremental restore is planned.

Can we use STDs as a target for Clone?

Yes, we can use standard or BCV as a clone.

How many CopyOnAccess sessionw symclone will support?

Up to 16 CopyOnAccess sessions

How many concurrent Full copied session clone will support?

Up to 4 concurrent Full Copied sessions

When we have to use –defferential option while create a clone session?

If clone recreate is planned or incremental restore is planned.

What will happen when we activate the clone session?

Places the target in the Read/Write (RW) state
Initiates copying if the -copy option has been specified in the symclone create command
Omitting the -copy option in the symclone create command defers data copying until either tracks on the source are written to or tracks on the target are read or written to

Explain Step by step procedure for TimeFinder Snap Operations?

Create
symsnap –g savedb create DEV001 vdev ld VDEV005 –svp save_db

Activate
symsnap –g savedb activate DEV001 vdev ld VDEV005

Restore
symsnap restore DEV001 vdev ld VDEV005

Terminate
symsnap –g savedb terminate DEV001 vdev ld VDEV005

How the copy session works in symsnap operation?

Once the Time Finder Snap session is activated:
When a host attempts to write to the data on the production volume, the original track is first copied to the “Save Area”, then the write is processed against the production volume. This process of pointers maintains the consistent, point-in-time copy of the data for the ongoing snapshot.

What is the background process while terminating the clone session?

When a copy session is terminated
The virtual device is made not ready
Tracks on the save device(s) are reclaimed if they are not referenced by any other copy session
The copy session structures are freed up

How many snapshots can be created from a single source volume?

Upto 15 snap sessions can be create with source volume.

How many snapshot can be created in multi virtual?

128

What will happen if save area is run out of space?

The target VDEV goes in Not Ready (NR) state, applications beware! Copy-on-write is disabled and the source track is changed.

What is the recommended size of VDEV?

1/600th the size of a source device

How the data will be stored in save devices in a save pool?

Data will be stored in a save pool as a round-robin manner. 

EMC Clariion - Possible Questions for Interview

Explain Clariion architecture?

The CLARiiON storage system is based on a modular architecture. The first building block of the architecture is the Disk Processor Enclosure, or DPE. The DPE houses the storage Processor(s) and the first Fibre Channel Arbitrated Loop (FC-AL) disks. Disk Array Enclosures (DAEs) are interconnected using Link Control Cards (LCCs).The module architecture allows the customer to add drives as needed to meet capacity requirements. When more capacity is required, additional disk array enclosures (DAE or DAE2) containing disk modules can be easily added. LCC or Link Control Cards are used to connect shelves of disks. In addition, the LCC monitors the FRUs within the shelf and reports status information to the storage processor. The LCC contains bypass circuitry that allows continued operation of the loop in the event of port failure.

Newer CLARiiON arrays have two processors per Storage Processor, and do not use a DPE. Instead, it utilizes an SPE or Storage Processor Enclosure. The SPE does not contain any disk modules, so it must have at least one DAE2 and a maximum of 16 DAE2s. CLARiiON Architecture is based on intelligent Storage Processors that manage physical drives on the back end and service host requests on the front end, be it Fibre Channel or iSCSI protocols. Storage Processors communicate to each other over the CLARiiON Messaging Interface (CMI). Both the front-end connection to the host and the back-end connection to the physical storage is 2Gb Fibre channel.

What are different types of Clariion models?

CX-200,300,300i,400,500,500i,600 and 700

CX3-10, 20, 40 and CX3-80

CX4-120, 240, 480 and CX4-960

AX Series

FC Series

What are the management tools for Clariion?

NaviCli

NaviSphere Manager

EMC Control Center

SymCli

Minimum number of disks required to create RAID 1/0 raid group?

4,6,10

What is Access Logix?

Access Logix provides LUN masking that allows sharing of storage system.

What are the significant features of Access Logix?

LUN masking.

Presents a virtual storage system.

Maps CLARiiON LUNs (FLARE LUNs) to host LUNs.

Manages the Access Control List.

Manages Initiator Registration Records - Access Logix database entries.

Why Access Logix has to be enabled?

If Access Logix is not enabled all LUNs are presented to all storage system ports. Any host that connects to the storage system will then have access to all of the LUNs on that storage system. In environments where multiple hosts attach to the storage system, this will cause problems. Windows systems may attempt to take ownership of LUNs belonging to other Windows systems, and Unix systems may try to mount Windows LUNs, Access Logix solves these problems by performing LUN masking – it masks certain LUNs from hosts that are not authorized to see them, and presents those LUNs only to the server(s) which are authorized to see them. In effect, it present a ‘virtual storage system’ to each host – the host sees the equivalent of a storage system dedicated to it alone, with only its own LUNs visible to it.

Another task which Access Logix performs is the mapping of CLARiiON LUNs, often called FLARE LUNs or FLUs, to host LUNs. It will determine which physical addresses, in this case the device numbers, each attached host will use for its LUNs. Note that this feature is configurable by the user through the CLI and the GUI. Access to LUNs is controlled by information stored in the Access Logix database, which is resident in a reserved area of CLARiiON disk - the PSM LUN. The Access Logix software manages this database.When host agents in the CLARiiON environment start up, typically shortly after host boot time, they send initiator information to all storage systems they are connected to. This initiator information is stored in the Access Logix database.

How can you check and enable Access Logix?

Right click on Clariion Array select Properties from the drop down menu.

Click on Storage Access Tab

Check whether Access Control Enabled

How many initiators can be connected per port in CX500 CX600?

CX500 – 64 Initiators/Port

CX600 – 32 Initiators/Port

What is CMI? Clariion Message Interface?

Storage Processors communicate to each other over the CLARiiON Messaging Interface (CMI).

What is SP Collects and how do you gather SP Collects?

Spcollect is a Storage Processor based perl script which gathers significant information from the Storage Processor and bundles this information for investigation by engineering.

navicli –h {ip} spcollect {eng mode password} – invoke the spcollects

navicli –h {ip} managefiles –list – to monitor the progress

navicli –h {ip} managefiles –retrieve –file {filename} – to transfer spcollect file to management host.

The managefiles command will transfer the data file to the Navisphere CLI directory where the command was invoked

Explain step by step procedure to assign a LUN to existing Host?

Will check is there any free space is available in existing RAID group as per the required LUN Capacity.

If not available create the new RAID group

Bind the LUN

Will go to the host’s storage group properties and open the LUN tab and add the newly created LUN

Explain step by step procedure for storage provision to the new host?

Installing HBA drivers in new host

Installing NaviAgent

Installing Powerpath if required

Creating Zone, add new zone to zone set, save and enable the zone.

Checking the host connectivity status in the array

Create a new RAID

Bind a LUN (create LUNs as per the host requirement)

Create a metaLUN if required

Create a Storage Group

Add Host and LUN in the storage group properties window

Reboot the host and check the LUN visibility at host-end.

What are pre requisites for LUN migration?

Migration moves data from one LUN to another LUN

Any RAID type to any RAID type, FC to ATA or ATA to FC

Neither LUN may be private LUNs or Hot Spares

Neither LUN may be binding, expanding, or migrating

Either or both may be metaLUNs

Destination LUN may not be in a Stora ge Group

Destination LUN may not be part of SnapView or MirrorView operations

Destination LUN may be larger than Source LUN

How do you create a Meta LUN?

Right Click on LUN > Select Expand > Expand Storage Wizard will appear click on Next > Select the Expansion Type (Stripped or Concatenate) and Click on Next > Confirm the Preserve Data dialog > Select the members (LUN) of Meta and click on Next > Select the User Capacity and click on Next > give the MetaLUN name, Default Owner, Expansion Rate, etc.. and click on Next > Review the Summary and click on Finish.

What is the recommended ration of Read and Write cache?

80% Read and 20% Write Cache

How do you troubleshoot if the Hosts are not registering issue?

1. Right click on clariion array and check the connectivity status whether the initiators are showing. If it is showing check whether the initiators are logged in.

2. If it is showing under connectivity status and registered status showing "NO" then you need to install Agent or else you need to register it manually.

3. If it is Registered and not logged in then you need to check the Zoning side and physical connectivity.

4. if the host initiators are not showing under connectivity status at all then you need check the zoning and physical connectivity. If possible remove the zone and create it back. Once you create the zone dont forget to Enable and Save the config. After this just refresh it.

5. Once all these tasks are fine then you can login to Navisphere and update the array once. Update is over then you can go to connectivity status and check.

What are the significant features of MetaLUN?

A metaLUN is created by combining LUNs

Dynamically increase LUN capacity

Can be done on-line while host I/O is in progress

A LUN can be expanded to create a metaLUN and a metaLUN can be further

expanded by adding additional LUNs

Striped or concatenated

Data is restriped when a striped metaLUN is created

Appears to host as a single LUN

Added to storage group like any other LUN

Can be used with MirrorView, SnapView, or SAN Copy

Supported only on CX family with Navisphere 6.5+

What are the significant features of FLARE operating systems?

FLARE Operating Environment runs in the CLARiiON Storage Processor. I/O handling, RAID algorithms.

End-to-end data protection.

Cache implementation.

Provisioning and resource allocation.

Memory budgets for caching and for snap sessions, mirrors, clones, copies.

Process Scheduling.

Boot Management.

What are the significant features of Cache Memory?

Cache memory on an SP performs two tasks:

Staging: Temporary buffering of current read and write data.

Always performed on each I/O.

Storage: Repository for frequently accessed data.

Maintaining copies of read and write data.

User must explicitly enable this (for both read and write).



Burst Smoothing - Absorb bursts of writes without becoming “disk bound”.

Write cache optimization.

Locality - Merge several writes to the same area into a single operation.

Increases write performance.

Immediacy - Satisfy user requests without going to the disks.

Read cache optimization prefetching of data for sequential reads.

What are the significant features of Clariion Event Monitor?

The Event Monitor GUI is integrated with Navisphere Manager.

Event Monitor is part of the Navisphere Agent.

Monitors for user-configurable events.

Reports those events in user-configurable ways.

May launch other utilities/applications.

Can send SNMP traps to Enterprise Management Platforms.

What are the Clariion Operating Layers?

EMC Control Center/ Clariion Based Applications

Navisphere Manager/NaviCli

FLARE Operating Environment

Clariion Hardware

Explain step by step procedure for LUN migration?

Right Click on the LUN and select migrate from the drop down menu.

Select the migration rate and click on OK.

We can check the status from migration tab in the LUN properties page.

What is the process of LUN Migration Operations?

Data is copied from Source LUN to Destination LUN

- Source stays online and accepts I/O



Destination assumes identity of Source when copy completes

- LUN ID, WWN

- Storage Group membership



Source LUN is unbound after copy completes

The migration process is non-disruptive

– There may be a performance impact

LUN Migration may be cancelled at any point

- Storage system returns to its previous state

What is Private LUN?

The LUN becomes private LUN when you add it to the reserved LUN pool. Since the LUNs in the reserved LUN pool are private LUNs, they cannot belong to storage groups and a server cannot perform I/O to them.

What is Reserved LUN Pool?

The reserved LUN pool works with replication software, such as SnapView, SAN Copy, and MirrorView/A to store data or information required to complete a replication task. The reserved LUN pool consists of one or more private LUNs.

How do you create a user and assign access rights?

Click on Tools > Click on Security > Click on User management

From the User Management windows Click on Add

Give the user name, Role, access level (Global or Local) and password.

How do you monitor Clariion alerts?

Using Clariion Event Monitor

How the Clariion Event Monitor works?

The Event Monitor GUI is integrated with Manager

Event Monitor is part of the Navisphere Agent

Event Monitor is designed to run in the background, without permanent supervision by the operator

Once Event Monitor is initially configured, there is no further need to run UI

Event Monitor relies on the text file navimon.cfg

Self-documenting text file included in Interface Kit

Does not require Event Monitor UI

Monitor Agents run on one or more hosts (or SPs) and watch over the storage systems

When an event is detected, the agent notifies the user As defined by navimon.cfg

Can send SNMP traps to Enterprise Management Platforms.

What are Vault drives and how much capacity they use?

Clariion Platform_____:Vault Drivers____:Vault overhead per drive

CX____________________:0-4______________:6.22 GB

CX3___________________:0-4______________:33 GB

CX4___________________:0-4______________:62 GB

AX4-5_________________:0-3______________:17.4 GB



Vault Drives:

All Clariions have Vault Drives. They are the first five (5) disks in all Clariions. Disks 0_0_0 through 0_0_4. The Vault drives on the Clariion are going to contain some internal information that is pre-configured before you start putting data on the Clariion. Vault Drives contains Vault area, PSM Lun, Flare database Lun and Operating System.



The Vault:

The vault is a ‘save area’ across the first five disks to store write cache from the Storage Processors in the event of a Power Failure to the Clariion, or a Storage Processor Failure.



The PSM Lun:

The Persistent Storage Manager Lun stores the configuration of the Clariion. Such as Disks, Raid Groups, Luns, Access Logix information, SnapView configuration, MirrorView and SanCopy configuration as well.



Flare Database LUN:

The Flare Database LUN will contain the Flare Code that is running on the Clariion. I like to say that it is the application that runs on the Storage Processors that allows the SPs to create the Raid Groups, Bind the LUNs, setup Access Logix, SnapView, MirrorView, SanCopy, etc…



Operating System:

The Operating System of the Storage Processors is stored to the first five drives of the Clariion.