VMs per Datastore Limit with VMFS and NFS?

[ktenzer]

My questions is as follows:

What is the best practice for the Maximum Number of VMs one should configure in a given datastore when using VMFS? If the VMs are not servers but rather desktop machines what is the maximum number? Also the same two questions if that datastore is NFS?

I have heard that due to VMFS locking the recommended maximum number of VMs in a server ENV is 20 per datastore and in a Desktop ENV (where all VMs are windows XP workstations) it is 40. The explanation I have heard for these limitations is VMFS SCSI 2 locking and the overhead involved. Since NFS does not have locking issues like SCSI, I would think the NFS limitations would only be based on number of IOs and Bandwidth.

Look forward to hearing what you guys think and what you recommend also any links to documentation would be greatly appreciated

Thanks in Advance,

Keith Tenzer

[wgardiner]

There's an interesting article that was just released discussing this:

http://www.gabesvirtualworld.com/?p=68

[kjb007]

The SCSI reservation and release is part of it, as is also that the I/O you get is per the LUN. Both make up the general recommendation to host around 20 servers per LUN. Now, you can have more than one LUN in your datastore, which isn't usually the recommended configuration. NFS does not adhere to the same recommendation, for the reasons you mentioned, file-level locking and I/O and bandwidth play a bigger part there. Also, NFS will not allow you to multipath your connections either, so you'll reach a theoretical max there as well. So, yes, you can have larger datastores and more VMs in NFS, but you will reach a max there as well, but that number is usually higher that as iSCSI or FC.

-KjB

[Jasemccarty]

I've always been amazed that we can get around 70-90 vmdk's (different guests) per LUN.

Of course, we aren't using NFS... But with 10GigE out there, who knows...

Jase McCarty

http://www.jasemccarty.com

Co-Author of the upcoming book, Essential VMware ESX