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persistent FCIDs

Unanswered Question
Nov 19th, 2010
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Under each VSAN in Domain Manager it shows that persistent FCIDs have been Enabled. Assignment is dynamic and in the Used column it shows that

some of the devices are True and others false. I didn't set this up and know a bit about Windows servers using persistent bindings but what does this mean? Is it something I should worry about as I have True and False and as I have only Windows boxes do I need it?

I remember reading about AIX servers needing persistent FCIDs, is it to do with that?


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Steven.langdale_2 Fri, 11/19/2010 - 07:59
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If you only have windows boxes, no you dont need to worry about it.


Some host O/S's use the target ports FCID as a way of referencing the storage, so if the FCID changes (switch reboot) they loose the disk and can't get the original luns back.  They tend to see "new" luns


Windows does not use FCID's.


You were nearly right with AIX.  For the past few years you have been able to turn on a feature called dynmic tracking which tolerates FCID changes.  Hving said that, there are ALOT of AIX hosts about with this feature disabled.


Steven

User_4444_2 Mon, 11/22/2010 - 04:59
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Thanks


It states in some of the Cisco documents that FL devices might have issues with Persistent FCID's. We have our Tape Library on the switches and the Robot is FL, will that cause a problem when moved? See below.


Note Persistent FC IDs with loop-attached devices (FL ports) need to remain connected to the same port in which they were configured.



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Michael Brown Tue, 11/23/2010 - 07:53
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HP-UX also has the need for the target FCID to remain the same. If the target FCID changes, like AIX, you would need to run IOscan to rebuild the lun binding in the operating system to account for the new FCID.  Since SAN OS 2.x the FCID mapping has been persistent meaning if a device logs back  into the same VSAN on the same swtich, the swtich will attempt to provide it with the same FCID as it was originally allocated at the first login.  As was pointed out, Windows, Linux and Solaris have no issues with a change in the target FCID.  HP-UX and most AIX implemtations would require an IOscan if the target FCID changes.

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