[Xen-users] NPIV & SAN Controller Failover

["Nick Couchman" <Nick.Couchman@xxxxxxxxx>]

I apologize if this is a little off-topic, but it does relate to Xen and using 
NPIV on Xen, so I think this is an appropriate forum for the question.  I've 
recently begun using NPIV for a couple of Xen PV domUs rather than traditional 
disk passthrough.  My reasons are primarily for performance - I'm hoping that 
NPIV has lower overhead and lower reliance on the resources of dom0 so that the 
performance in the domU is better.  In any case, I did a firmware update on my 
SAN controllers last evening, an upgrade that was not supposed to impact 
connectivity to the SAN, as I have redundant SAN controllers and the upgrade 
reset the controllers in sequence so that hosts would still be able to talk to 
the SAN.  This worked perfectly for all of my physical machines and virtual 
machines, except for the ones using NPIV, which crashed miserably.  I ended up 
having to reboot my dom0/host to get it to see the disks correctly.  I'm 
wondering if anyone has any experience with this, or any hints on configuring 
NPIV correctly for a fail-over situation?  My disk configuration is as follows:

disk=[ 'phy:/dev/disk/by-id/scsi-36000d31000083c0000000000000000cb,xvda,w', 
'npiv:2001000dec8f9741-8888888810002000-8888888800000002-5000d31000083c0a-1,xvdb,w',
 
'npiv:2001000dec8f9741-8888888810002000-8888888800000002-5000d31000083c0a-2,xvdc,w',
 
'npiv:2001000dec8f9741-8888888810002000-8888888800000002-5000d31000083c0a-3,xvdd,w',]

As you can see, I'm attaching one disk via passthrough (my system disk), and 
the other three via npiv (data volumes).  The fourth and final set of hex 
numbers there is the WWN of one of the FC ports on one of my SAN controllers.  
I'm still a little fuzzy on how my SAN handles the failover, but I'm wondering 
if the fact that I'm pointing at a specific WWN is causing problems?

Any help/advice would be appreciated!

Thanks,
Nick



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