EVA4400 & CA

 
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Rob Crooks
Frequent Advisor

EVA4400 & CA

I am looking for clarification on something that recently happened with my EVA that has me really confused. It has to do with CA and Failover. I just upgraded to unlimited CA on my 2 EVA4400's and noticed that I had the source and destination reversed on a replication that I had setup a few weeks ago. I needed to test out my DR plans, so I verified that both the source and destination were presented to the (in this case) windows cluster nodes.
To failover the volume, I followed these steps,
1) Stopped the disk cluster resource and then name resource in Windows Cluster Manager
2) On the destination EVA, I failed-over the volume.
3) I then opened Disk Manager and rescanned the disks, expecting to find a new volume to assign it the same drive letter

The thing is, I didn`t see a new volume. I restarted the disk resource and then the name resource and everything came up fine.

The confusion I have is that I fully expected Windows to see the source volume of the replication pair to be new and unknown, as it comes from a different array. But it didn`t and I would like to know if anyone knows why.
This is an entirely welcome behaviour, albeit unexpected.
I suspect it might be from the MPIO driver, but I`m not sure.
Is this something I can depend upon when developing my DR procedures?
3 REPLIES 3
Amar_Joshi
Honored Contributor
Solution

Re: EVA4400 & CA

It depends on how the Windows cluster was created. If the DR nodes are aware of primary cluster then the disk signatures are verified and will not be treated as new volumes. I have seen some setup where DR cluster is not configured correctly and their DR process has to write new disk signatures at DR clusters before they can use the replica disks.
Rob Crooks
Frequent Advisor

Re: EVA4400 & CA

Actually, your response makes quite a bit of sense. I never considered the disk signature. I'm going to test this on a MSSQL cluster and see if I can replicate the situation.
Thank you for the reply.
Rob Crooks
Frequent Advisor

Re: EVA4400 & CA

Answer provided points me in the right direction.