Hey guys, thanks for taking a look at this issue ... I am looking for some ideas.
I have 2 virtual machines, running Windows 2008R2. They have MSCS set up and working as a CAB (cluster across boxes). I am using a VNX 7500, fibre channel drives and physical RDMs. This is on an 8 node, ESXI 5.1 v1117900 implementation. Functionally everything works just fine.
The problem is that the performance is very poor on only the RDMs that have been added to the MSCS cluster. I can take the same drive, remove it from the cluster, run IOmeter and it is fast. I add it to the MSCS cluster, leaving it in available storage, and it is 1/15th the performance IOPS. Delete the drive from MSCS and it goes back to performing as usual.
I've tried different SCSI controllers (Paravirtual vs LSI Logic SAS) and it didnt seem to make a difference. I have physical MSCS clusters that don't seem to exhibit this kind of performance issue, so I am wondering if there wasn't something goofy with the MSCS over virtual machines configuration.
I have already implemented this KB article: http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1016106
I was seeing that poor bus rescan performance issue until I set the RDMs as perennially-reserved but it hasn't been an issue since I implemented the fix.
Any help or suggestions is appreciated ...
Thanks,
-dave