Windows Swap File Location

[jfierberg]

Are there any performance hits or configuration issues if I configure a vm to have its OS vmdk on a NFS volume and its OS Swapfile HD on an iSCSI lun?

[James Bowling]

I would check out the Performance Best Practices Guide, specifically starting around page 24:

http://www.vmware.com/pdf/Perf_Best_Practices_vSphere4.0.pdf

[jfierberg]

Thanks for the reply.  The pages in the Best Practice pdf seem to refer to ESX swap files not the Windows PageFile.  I am assuming that there is not much of a performance hit for a vm with vmdks on two different storage platforms.  This is what I need to nail down though.

[James Bowling]

Placing the virtual machine’s swap file on a high speed/high bandwidth storage system will result in the smallest performance impact. The swap file location can be set with the sched.swap.dir option in the vSphere Client (select Edit virtual machine settings, choose the Options tab, select Advanced, and click Configuration Parameters). If this option is not set, the swap file will be created in the virtual machine’s working directory: either the directory specified by workingDir in the virtual machine’s .vmx file, or, if this variable is not set, in the directory where the .vmx file is located. The latter is the default behavior.

You are correct that would not be much of a performance hit.  I have had a couple of different deployments where we had OS disk on cheaper SATA drives and the data on a different storage type.  So yes, it is possible, will you see much of a performance increase, probably not.

[DSTAVERT]

An SSD dedicated to swap files might provide a performance gain. Testing could confirm.

http://vpivot.com/2009/12/24/solid-state-disks-and-host-swapping/

[mcowger]

If you are swapping enough that SSDs vs. spinning media makes a difference, I think you have a bigger problem - you've overcommited your memory far too much.                   

[James Bowling]

I have to agree with what mcowger is saying.