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SAN volume offline until change in storage processor

Posted on 2010-09-16
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Last Modified: 2012-06-27
We have a customer who is using an EMC AX100i SAN that has two storage processors on it. This same SAN also has two volumes defined. Typicaly, we have one volume on one SP and the other volume on the other SP. Recently, after a reboot the volume on the server will be listed as "Unrecognizable" and won't become active until we move the volume on the SAN from one SP to the other. We will do nothing with the iSCSI initiator and the volume will appear on the server shortly after the storage processor change. There is no support agreement on the SAN and nobody, prior to our involvement, ever set up an account with EMC for support. So, going to EMC is not an option. I am curious if anyone has ever seen this before and, if they have, what did they do to correct it?
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Question by:DavidBCS
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Duncan Meyers earned 500 total points
ID: 33699563
The reason this is happening is that there is nothing telling the AX100 to fail the LUN over. That would be handled either by PowerPath (PowerPath is free for path failover only. You pay for path balancing), or by other software such as Symantec Storage Foindations (also a freebie for no more than two processors and four volumes. Alternatively, you can open the LUN properties and set the failover policy to "automatic".
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by:DavidBCS
ID: 33718561
Would enabling Multi-path on the iSCSI initiator help in this situation? It is not currently set. Also, since each volume is only bound to one storage processor on the SAN and since there is no auto-failover value to be set on the SAN, could I accomplish the same thing by telling the iSCSI initiator to only attach to the SP hosting the volume instead of looking for both?
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by:Duncan Meyers
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>Would enabling Multi-path on the iSCSI initiator help in this situation? It is not currently set.
Yes, as part of the fix - but unless the LUN is explicitly told to fail over, it won't. You also need to set teh LUN failover policy to automatic as described above. Th estorage processors won't fail over the LUN unless it's told, or if it doesn't detect I/O on the other storage processor.

>Also, since each volume is only bound to one storage processor on the SAN and since there is no auto-failover value to be set on the SAN, could I accomplish the same thing by telling the iSCSI initiator to only attach to the SP hosting the volume instead of looking for both?
My apologies - got the name wrong. The setting is for auto trespass - trespass is failover in CLARiiON-speak.
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by:DavidBCS
ID: 33724891
Is the auto-trespass feature something that is licensed? I don't have that option on the SAN under the WebUI. I think this particular SAN may be a Dell re-brand. Could it be possible that it is lacking some features as a result? Pardon my ignornace as I am not familiar with this product since I mainly work with HP SANs and we inherited this when we took over this account.
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by:Duncan Meyers
ID: 33731913
Sorry - having one of those weeks. Look at the LUN properties dialogue box and check the "Enable Auto Assign" box. The LUN will automatically trespass when:
SP reboot or failure
Storage-system reboot or power failure
Server I/O trespassing to the peer SP

With auto assign enabled, if the SP that owns the LUN fails and the server tries to access that LUN through the second SP, the second SP assumes ownership of the LUN to enable access. The second SP continues to own the LUN until the failed SP is replaced and the storage system is powered up. Then, ownership of the LUN returns to its default owner. If auto assign is disabled in this situation, the second SP does not assume ownership of the LUN, and access to the LUN does not occur.


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by:DavidBCS
ID: 33749098
OK... It must be a licensing issue or something because I have none of those features on the SAN WebUI for auto-trespass or anything to that effect.. Perhaps it's because it is running Navisphere Express and this is a dumbed-down version... I guess I'll live with it... The customer does not want to pour anymore money into this product platform.

Thanks for your assistance. You've given me some good things to look at.
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by:DavidBCS
ID: 33749107
I have all the information I need at this point.
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by:Duncan Meyers
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Thanks! Glad I could help.
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