Wednesday, June 6, 2012

DMX-4 Interview Questions (Which I got from Net, tried to answer some of them)

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

 Cache directors -8
 Front-end directors -8
 Back-end directors -8

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

  Mainframe CKD devices:
    ESCON (EA)
    FICON (EF)
 Open Systems FBA
      Fibre channel (FA)
      ISCSI (SE)  etc

3.What are the Management Tools for DMX?

EMC Control Center (ECC)
EMC Solutions Enabler
EMC Symmetrix Performance Analyzer

4.What are the major components of System Bay and Storage Bay?

System Bay:

Directors and Memory boards, FANS, KVM, SPS, UPS, Power Supplies, XCM boards

Storage Bay

DAEs, BBU (Battery Backup Unit),SPS,LCC Link control card
5.Explain Enginuity Operation layers
         Symmetrix-Based Application
         Host-Based Symmetrix Application                    -1
         Independent Software Vendor Application

          EMC Solutions Enabler API       -2

          Symmetrix Enginuity Operating Environment  Functions  -3

          Symmetrix Hardware  -4

6.How do you calculate number of cylinders for 50GB LUN?

   15 tracks -1 cylinder
   64 blocks – 1 track
   512 bytes-1 block
   1024= conversion of bytes to kb to mb to GB
   GB=cylinder *15*128*512/1024/1024/1024-DMX3 DMX4 VMAX
   GB=cylinder *15*64*512/1024/1024/1024 -DMX DMX2

    so 54613.3 cylinders.

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

  symconfigure –sid 1234 –cmd “add dev X to meta Y”; commit

8.Briefly explain the DMX-4 supported Device types?

Mainframe and Open systems devices

9. What are the RAID levels DMX-4 Supports?

RAID 0, RAID 1, RAID 5, RAID 6, RAID 1/0

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

 C:\Program Files\EMC\SYMCLI\bin>symdisk -sid 2258 -failed list

Symmetrix ID                 : 00019010XXX8

No devices were found

C:\Program Files\EMC\SYMCLI\bin>

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


12.Host is unable to see the storage, what may be the problem?

 Host WWN issue, Zoning issue, switch port failure, connectivity issue, SAN disk issue

13.What is VCMDB and How do you take the backup?

The Symmetrix Volume Configuration Management (VCM) database stores access configurations that are used to grant host access to logical devices in a Symmetrix storage array. The VCM database resides on a special system resource logical device, referred to as the VCMDB device, on each Symmetrix storage array.

Information stored in the VCM database includes, but is not limited to:
Host and storage World Wide Names
SID Lock and Volume Visibility settings
Native logical device data, such as the front-end directors and storage ports to which they are mapped
Masking operations performed on Symmetrix storage devices result in modifications to the VCM database in the Symmetrix array. The VCM database can be backed up, restored, initialized and activated. The Symmetrix SDM Agent must be running in order to perform VCM database operations (except deleting backup files).

Backup the VCM database
      # symmaskdb backup

14. What is stripping and what is Concatenating?

    Concatenating- First byte of data at the beginning of the first device and addressing   continues to the end of the first device before any data on the next device is referenced.

 Stripping-divides the data to a series of stripes.

15. What is Read Hit and Delayed fast 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

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 directors then destage the Least Recently Used data to disk. When sufficient global memory space is available, the channel directors reconnect to their channels and process the host I/O request as a fast write. The Symmetrix system continues to process read operations during delayed fast writes. With sufficient global memory present, this type of global memory operation rarely occurs

16. What are the Symmetrix Business Continuity Tool

Time finder


17. By using what symcli command we can check the HBA details and physical details

     symmask list hba                   –list local host hba details
     symmask –sid  1234 –wwn wwn list logins
     symmaskdb –sid 1234 –host name list capcity (not in VMAX)

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

    symamsk –sid 1234 list logins –dir 10e  –p 1

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

    Symmaskdb –sid 1234 –host name list capacity

20. What is the purpose of bin file in SAPAPI database?

  It contains the configuration information for a symmetrix.
    The file defines the
                   Physical hardware configuration
-Physical Drives
 Logical Storage configuration;

Emulation,number ,size and data protection schemes for logical volumes.

Operational parameters and features.

Located on each director and in  SP

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

    Host WWN details.

    Host and SAN connectivity to Fabric Switch

    Type of storage needed(Tier 1,Tier2 ,Tier3 )

    Size of the LUN

22. How do you check the login hosts in the Array?

    symmask –sid 1234 list logins

23. Explain Rule 17 in DMX?

Rule 17 is mainly for DA, Director pairing, along with dual ported drives and the use of the Port Bypass Cards, now provides redundancy for a disk drive failure.Directors are paired processor to processor using the rule of 17.Directors 1 and 16 are paired and directors 2 and 15 are paired. The same concept is followed on FA even if it is not mandatory. Normally channel directors are installed in pairs ,providing redundancy and continuous availability in the event of repair or replacement to any one channel director.
So by making the directors in sum of 17, both the directors would fall under different power zone and if one goes down also the data to be served.

What is the FAN-IN and FAN-OUT ratio of DMX-4?

What is the maximum hyper size in DMX-4?

 How many hypers can create in a Single disk?

How many members can contain in one meta?

 How many LUN IDs available per port?

What Dynamic LUN addressing?

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

What are Vault drives and Hot Spare?

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

How do you check the back-end Operations on Symmetrix Array?

What are the service states of a device

How do you reserve the devices?

What is Tiering and how do you create the Disk Groups

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

How do you check the particular disk is connected to which DA Port and it is resides in particular DAE?

What is drive looping?

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

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

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

Explain step by step to provide storage to the Host?

What is Thin Provisioning?

 How do you create thin pools and thin devices?

 What are the steps for storage reclamation?

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

  How do you increase the mirror positions?

How do you convert the One device type to another?

 What is FA Port Flag and how do you set the FA port flags?

How do you setup the Symmetrix metrics?

How do you check the configured environmental variables?

What are the External locks and how to check?

How to monitor performance of EMC Symmetrix?

How do you check performance statistics of a particular director port?

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

How do you check the back-end I/O requests of selected disk?

What are the available performance information types in SYMSTAT command?

What is symmetrix optimizer and how it works?

What is Symmetrix QoS and how it works?

What is the purpose of Symmetrix Change Tracker?

 What is Dynamic Cache Partitioning?

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

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

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

 How do you check the audit logs on symmetrix array?

 How do you activate the auditing on symmetrix array?

What is Symmetrix ACL?

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

 How do you take the backup of ACLs?

What is Symmetrix User Authorization?

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

 How do you perform backup and restore user authorization information?

What are the services of symcli?

Explain step by step procedure to setup new host?

What are the Symcli Base Management Commands?

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

1 comment:

  1. Hi All,

    For more questions and Answer, pls refer below link.