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Disabling mirrorcache on production VDISKS

mikewjohnston
Occasional Contributor

Disabling mirrorcache on production VDISKS

I am running vcs3.110 on an EVA 5000, and I am replicating asynchronously via CA to another EVA 5000 over a 1Gb FCIP link.

I have a three node, Redhat 2.4.21-51.ELsmp Oracle RAC cluster and I am trying to squeeze as much I/O performance as I can out of the EVA. There are processes that run periodically that are very write intensive, and it causes iowaits to spike for extended periods of time and my CA replication only exacerbates the issue since the write buffer in cache for CA replication is so small on the 5000.

At any rate, now that you have a clear picture of the environment, my problem is this. I want to disable write cache mirroring on the luns for the RAC cluster, but I have snapshots and they are currently in DR groups for replication.

Short of deleting snapshots and deleting DR groups, is there a way to disable write cache mirroring? I get the following errors when I try to execute my scripts, so I assumed that I had to remove these replication and snap relationships prior to the cache settings change:

This error occurred when I tried to turn off cache mirroring on a replicated and snapped VDISK.

Error: Error cannot modify object properties. [Operation rejected - The Vdisk has a sharing relationship with another object]

...and then I tried to turn off write cache on a VDISK that was replicated but not snapped and I got this error...

Error: Error cannot modify object properties. [Cannot add or remove DR group member. Mirror cache must be active for this Vdisk. Check controller cache condition.]

...and lastly...I tried to turn it off on a generic VDISK that did not have any relationships and I got this error:

Error: Error cannot modify object properties. [Objects in your system are in use, and their state prevents the operation you wish to perform.]

...Here is my basic syntax. Nothing wrong here.

SET VDISK "\Virtual Disks\XXX" MIRRORCACHE=notmirrored

I'm not sure what the deal is, unless you can only turn off write cache mirroring when a lun is unpresented and/or there is no I/O. If anyone can verify that for me, that would help also...

As an aside to this issue, if anyone has replicated with CA on a 5000 asynchronously and had source write performance issues that appear to send the replication into a synchronous-like state, please respond as well. I would be curious to hear anything that you have done to mitigate the performance issues.
1 REPLY
gstonian
Trusted Contributor

Re: Disabling mirrorcache on production VDISKS

Sorry for the very late reply to this but I was just doing something similar and discovered this thread.

The LUN has to be unpresented before you can turn off the mirroring