Maintaining Same FCID with a port vsan change

Unanswered Question
Aug 15th, 2010

I recently went through a VSAN consolidation where i took 2 VSANs and combined them into a new VSAN.  The problem i have run into is that even after making sure that the domain id's of the source and destination VSANs were the same, the fcid's of the individual ports that were in the source VSAN changed when i moved them into the new VSAN.  For HP-UX systems, this is a huge issue because HP-UX uses the fcid of the storage port to generate it's HW addresses for disks.  With the fcid of the storage ports changing, this caused all of the HP-UX systems to reconfigure thier HW addresses and ended up causing some systems to crash.

To make it worse, when i try to go into domain manager in device manager to change the fcid back to what it was, the switch has already reassigned the original fcid to something else.  And even when i find one that hasn't been, and i try to change it, it complains about a duplicate WWN.  there are no duplicate WWN's.... :-(

Question1:

Is it possible to maintain the same FCID when changing the vsan assignment of a port?

Question2: I noticed that persistant fcids is enabled for both domains.  do i simply need to disable that in order to change the fcid back to what it was?

Thanks!

Bob

I have this problem too.
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Steven.langdale_2 Thu, 08/19/2010 - 10:40

Bob

I've not done this in a while so going from meory here....

Q1:  Yes it is as long as the domin ID is the same (which it looks like you've done).  I think you need to remove the device from the SAN before you can delete the FCID.  Also, I think you need to add the new FCID before you reconnect it.

Q2: You want persistant ID's on, without that a switch restart will mean all new FCID's all over again.

Having said all of that, I've migrated HP-UX boxes (and older AIX boxes without port tracking enabled) and not had to maintain the FCID.  I assume you have/had 2 fabrics and the HP boxes are dual attached?  IF thats the case, and you have working multipathing, then whilst you do have to do some remedial work on the boxes, you will not have system crashes / loss of access to data.

Steven

Steven.langdale_2 Thu, 08/19/2010 - 10:40

Bob

I've not done this in a while so going from meory here....

Q1:  Yes it is as long as the domin ID is the same (which it looks like you've done).  I think you need to remove the device from the SAN before you can delete the FCID.  Also, I think you need to add the new FCID before you reconnect it.

Q2: You want persistant ID's on, without that a switch restart will mean all new FCID's all over again.

Having said all of that, I've migrated HP-UX boxes (and older AIX boxes without port tracking enabled) and not had to maintain the FCID.  I assume you have/had 2 fabrics and the HP boxes are dual attached?  IF thats the case, and you have working multipathing, then whilst you do have to do some remedial work on the boxes, you will not have system crashes / loss of access to data.

Steven

Michael Brown Thu, 01/27/2011 - 13:29

You can display what the current 'persistent fcid database' looks like by issuing 'show run' on the MDS.

If you see an entry that needs to be changed, it must be removed first as was mentioned.  If the device is currently logged in, it must be logged out before you can delete the static fcid entry.  Once the entry is put back into the config, if that PWWN logs into the correct vsan, it will be assigned the persistent fcid entry entered into the switch configuration.

The host side is not where the fcid has to be maintained, it is on the storage side.  The storage fcid is what hp-ux and older aix operating systems use to build the internal lun binding.  When this fcid changes is when these OS have to be reconfigured to adjust the lun binding to include the changed fcid.

wosuser2009 Fri, 01/28/2011 - 05:40

Thanks for the feedback everyone, but this done now, and i'm happy to say it went pretty smoothly.  What i didn't know then was that fabric manager gives you the ability to prepopulate the vsan fcid database tabels with the fcids that you want. But you need to make sure that those fcids are set to static in the original vsan.  Otherwise they come over as dynamic and will change on you even though you've set it before hand.  As long as you watch out for that, your new vsan will contain the exact same fcids that it had in the old vsan.

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