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SAN storage Interview question

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

Question by:belranjan
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Expert Comment

by:Duncan Meyers
ID: 16389294
What sort of thing do you mean?

Expert Comment

ID: 16390933
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.


Expert Comment

ID: 16390938
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!!
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Author Comment

ID: 16398288
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

Expert Comment

ID: 16398368
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

ID: 16400402
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

ID: 16400425
U have any idea on ibm flash copy and volume copy

Accepted Solution

prof666 earned 300 total points
ID: 16402353
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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