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Restoring Tru64 UNIX from a replica of its disk - CA/EVA

SAKET_5
Honored Contributor

Restoring Tru64 UNIX from a replica of its disk - CA/EVA

Hi All,

I present this question specifically for Tru64 UNIX as we have a large number of these hosts. However, I am currently testing the same concept on RedHat Linux, Windows 2003 & possibly Sun Solaris as well. I might post my results on these other OSs on the forum once I get them.

As the procedure is detailed, I have attached a document which explains the steps of our tests and the bottlenecks.

In brief, a host running Tru64 UNIX (V5.1B) booting off the SAN (EVA 5000; VCS 3.020)has a couple of Vdisks presented to it. It uses one of them to boot and the other one is there for its data partition. These two Vdisks are replicated (Failsafe Mode:Disabled; Write Mode: Synchronous) to another EVA 5000 Array (destination EVA) running the same VCS Version 3.020. To simulate the failure of an EVA (primary EVA), the host is shutdown, DR Group deleted, fabric zoning re-configured to allow the host in question to access the destination
EVA and to revoke access to the primary one.The replicated Vdisks "WriteProtect" is disabled, WWN of the LUN is the same on the replicated Vdisks and they are allocated the same LUN and presented to the same host--->the host is configured at the SRM layer for the disks from destination array--->the result is the host boots off successfully however the disk device name changes!!!

This is the bit we are expecting to not go through....i.e. in a nutshell if the WWN of the LUN is the same between the original disk and replicated Vdisk and the LUN is the same (although we notice that the UUID changes on these disks and ofcourse the Controller WWN at the SRM layer is different)....why does the disk device name change??

Surely, there is gotta be a transparent operation or someone has tested a smooth restore of systems using CA!!

Any thoughts guys?

P.S. A hp call in this regard is in its early stage!

Have a read of the document...some of you might find the results interesting!!

Regards,
Saket.
2 REPLIES
Devesh Pant_1
Esteemed Contributor

Re: Restoring Tru64 UNIX from a replica of its disk - CA/EVA

Saket,
Unfortunately the DDR database in Tru64 is such that somehow even though the WWNs for the LUN remain the same, it recognizes that the FA on the EVA has a different WWN and treats it as a different device. You are able to boot off of the first device since the DDR has not come into play yet.

The best way to get around would be to have dfsmgr -m /dev/disk/dskxx /dev/disk/dskyy
where dskyy is what you want it to be and dskxx is what it comes up with.

I have faced this in our Disaster recovery drill.

thanks
DP
Eric van Dijken
Trusted Contributor

Re: Restoring Tru64 UNIX from a replica of its disk - CA/EVA

Maybe i didn't understand your procedure completly, but did you use the "CA failover" on the EVA vdisks?

I have used that in the past and after the system rebooted, All was fine again (but running on the other EVA)
Watch, Think and Tinker.