Virtualising Exchange 2010 - getting the right IOPs

[aetius1980]

Hi,

I'm virtualising Exchange 2010. I've worked out my iops to accomodate several thousand users, the disks I have, once accounting for RAID 10 overhead just about cut it in terms of IOPs for full capacity.

My data store requirements are several terrabytes.

My question is if I use VMFS, being that there's a layer of abstraction to the underlying storage, will I still get my raw iops at the back end?

Would I better off using RDMS in terms of IOPs?

Thanks

[aetius1980]

Ah man, no answers, 

[sparrowangelste · Accepted solution]

best performance would most likely be rdm but looks like vmfs can keep up

"There are no concrete recommendations for using VMFS or RDM in Exchange deployments"

http://www.vmware.com/files/pdf/Exchange_2010_on_VMware_-_Best_Practices_Guide.pdf

[MKguy]

RDMs inherently performing better than VMDKs on a VMFS is an old myth popping up every now and then. This been disproven a few times already, for example here:

http://www.vfrank.org/2011/03/22/performance-rdm-vs-vmfs/

http://www.vmware.com/files/pdf/performance_char_vmfs_rdm.pdf

Bottom line: There is no general performance benefit, but beware of the limitations RDMs (especially physical ones) could incur. The only real reason to use physical RDMs is Guest-clustering or when you have to bypass the 2TB limit for a single volume to a guest.

[cabraun]

"Bottom line: There is no general performance benefit, but beware of the limitations RDMs (especially physical ones) could incur. The only real reason to use physical RDMs is Guest-clustering or when you have to bypass the 2TB limit for a single volume to a guest."

Or if you have a requirement for SAN based snapshots / snapclones of the volume.

[mcowger]

Or you are doing application aware replication of the volume...

[aetius1980]

Thanks for the feedback guys.

I'm using Vmware 5 and don't have a need for san snapshots or clustering. Think I'll go VMFS

Cheers