ESX Swap file/VM Page file location question

ESXi 5 Cluster
NetApp FAS3240 Cluster (Active/Active)
NFS Datastores

I'm going through the best practices documentation from NetApp concerning vSphere and Storage (TR-3749).

NetApp recommends storing the VM Swapfile on a centralized datastore for disk cost savings (snapshots and replication). This setting would be set at the host level. When going into the settings at the cluster level, VMware "recommends" saving this within the same directory as the VM.

Anyone have experience with this? As in pros and cons? I can see where this could degrade the performance of vMotion, but other than this I was looking for some input from people who have run this in production.

Also, what are your thoughts on also moving the VM's pagefile (OS) to a separate VMDK that is located on a centralized datastore as well? Same thought process here.. disk savings is nice, but don't want to introduce stability issues (if any).
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MMRNLAITAsked:
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
If VMs start to swap, you want to put the ESX Swap and VM Page files on the fastest datastore as you can.

Swap-In functions is what causes the most performance issues.

You may want to look at consumer SSDs - 32GB just for Host Cache Configuration now supported in ESXi 5.0 for this very purpose, SSD have far better latency, between disks and RAM for Swap file usage.

Also ensure, that Pagefiles are correctly set in the VM, and for performance again, allocate on fast datastores.

Place guest’s swap file/partition on separate vdisk
• Allows you to monitor guest swap activity through virtualDisk stats

see here

http://www.virtuallyghetto.com/2011/07/how-to-automate-host-cache.html
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MMRNLAITAuthor Commented:
We have zero contention with our cluster in regards to memory resources. I was more interested in disk cost savings in regards to replication. We have limited bandwidth to our DR site and I want to decrease our snapshot data footprint as much as possible.


But you bring up an interesting point about using SSDs. In general can we gain performance by using them for host cache?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Yes, Increased Performance, for very little space used.

Overcoming slower latency in using traditional disk, where SSD have much better performance in this area.

SSD is just for Host Cache. So 32GB will be ample for most sites.
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MMRNLAITAuthor Commented:
one more question, would there be an issue with creating one datastore for both the swapfile and pagefile on all my VMs?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Certainly not, but make sure you do not have performance issues with it, otherwise ALL VMs will be affected.
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MMRNLAITAuthor Commented:
certainly not? As in yes? or no?

=)
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
No issues, but monitor performance of the disk and datastore.
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