SAN storage Interview question

Posted on 2006-04-05
Last Modified: 2013-11-15
Can any one help me on san storage interview question with answers

Question by:belranjan
    LVL 30

    Expert Comment

    by:Duncan Meyers
    What sort of thing do you mean?
    LVL 6

    Expert Comment

    You mean questions to ask a prospective employee?

    1) Q: Describe the difference between RAID0,1 and 5 and name 3 SME type arrays
        A: 0 is plain striping typically with 32KB,54KB or 128KB stripe size.
        A: 1 is mirroring
        A: 5 is striping with parity
        A: HP-EVA, EMC-Clariion, HDS-Thunder, IBM-FastT

    2) Asking him to describe the function of the following in a SAN switch :

    Nameserver - (Answer: it processes the devices in SAN and provides the zone member details to the host.)
    Aliasing - (Answer: attach useful names to WWN's and ports for easier management)
    ISL- (Answer: Inter switch Link, to join many switches together in a fabric)

    3)Q: Ask them to explain oversubscription on ISL's
        A: Ratio of incoming connections over the ISL to the available bandwidth on the ISL. (Hint: they should state that 7:1 or less is generally accepted as good practice!!!)

    4)Q: Name 4 types of SAN architecture types
        A: Core-edge, Full-Mesh, Partial-Mesh,Cascade

    5)Q: What is the best practice for adding a new switch to and existing SAN?
        A: Steps below:
              1) Give the switch an IP address via serial cable, and link into network
              2) Log on to switch and clear down any configuration (zones, zonesets, aliases, cfg options etc..)
              3) Disable all ports on the new switch
              4) Same the configuration definition of the current SAN to FTP BEFORE any merge is attempted.
              5) Cable up however many ISL's to the core switch (or whatever architecture you have designed)
              6) Make sure all new ISL ports are either set to auto or have been manually set to E_Port.
              7) If going long distance make sure both ends of the new ISL have the correct buffer credit setting and licenses.
              8) Finally enable the ISL port and make sure the switch is integrated to the SAN and is see in the fabric and that no segmentation occurs.

    That should be enough for a basic interview. None of the above should be hard for anyone who has worked in the SAN market place before.

    LVL 6

    Expert Comment

    duh..I hate not being able to edit posts....Answer on stipes in question one should read:

    A: 0 is plain striping typically with 32KB,64KB or 128KB stripe size.

    64KB not 54KB....sorry fat fingers today!!

    Author Comment

    Can u give some advance example questions.

    I having one doubt in san.

    If iam configuring three servers and having storage in san box which is connect through a san switch. Let say one hp server and another two r IBM. My question starts here suddenly my HP server os corrupted. Is it possible to map the HP Lun on ibm server. And make all our user to access the file share on IBM Server. And what steps to take to complete the configuration
    LVL 6

    Expert Comment

    OK, so if I read your question correctly, you want to mount the HP DATA volumes (not OS volumes) onto the IBM (AIX I assume?). This is totally possible as long as the data volumes are built using a filesystem that both OS's understand (say XFS or JFS). It should be a simple matter of re-doing any LUN masking on the SAN storage array, and then doing a bus rescan on the AIX (cfgmgr) to pickup the new disk then use either SMITTY or cmdline to mount it up.

    As for an advanced question:

    Q: Describe the composition of a fibre channel frame
    A: From start to finish:
                     1) Start of Frame Locator (1 word)
                     2) Frame Header (includes Destination_ID and Source_ID....24bytes/6 words)
                     3) Data Payload (encapsulated SCSI instructions can be 0-2112 Bytes in length. If less than 2112, then remainder upto 2112 is filled with padding )
                     4) CRC (error checking 4 bytes)
                     5) End Of Frame (1 word)

    Q: Name the 7 common frabic services as defined in the ISO fibre channel standard and their Hex addresses.  (Very hard question !!!! Not many outside of the vendors or certified experts will get this one!)
    A:  FFFFFA - Management Server
         FFFFFB - Time Server
         FFFFFC - DIrectory Server
         FFFFFD - Fabric Controller
         FFFFFE - Fabric Login Controller
         FFFFFF - Broadcast Server
         FFFFF8 - Alias Server

    Author Comment

    What i understand is that. If my os go down i can remount the data volumes on other server. If it windows means. Same thing redo lun masking and scan for new disk in disk management to mount the drives

    Author Comment

    U have any idea on ibm flash copy and volume copy
    LVL 6

    Accepted Solution

    If you have additional question I suggest you ask it in another pointed Question as you may get a better response (My IBM array experience is limited..I've mainly done EMC and HDS).

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