swap file storage

[im822]

I have asked the Dell VMware guy as well as other consultants. No one has given me a strait answer.

My question is how to Enterprise environments configure the storage of Guest Swap files locations in vcenter ESX clusters?

Do they use local storage on each ESX host?

Do they use SAN storage?

I have two vcenter ESX clusters. One ESX cluster is configured to use one SAN Data store. The other ESX cluster is set for "store the swap file in the same directory as the virtual machine"

I have a vcenter cluster with three esx hosts. Right now I am using a Fiber Channel Lun to assign the storage of VM guest swap file locations to this one LUN.

I am considering using a group of SATA drives in my EMC storage as a lun to keep these VM guest swap files. What are your thoughts on risk for performance issues?

I

[Viperman]

They haven't given you an answer because there really is no "best practices" answer.

So, lets do a little education first.  When does a virtual machines ever use the vswp file?  Answer: When the ESX host is running out of physical memory, or if you set a limit on the VM.  The VM will initially use the balloon driver if VMware Tools are installed, then once they max out it will start to use the vswp file if the host is low on physical memory.  One of the big keys:  If your host has plenty of physical memory this file will hardly ever be used. 

That being said.  How much performance do you need for a file that will never be used?

So.  What do most Enterprise companies do?  Answer: Nothing.  Leave it in the default location which is stored with the VM.  Why?  Most of them don't know any better.  Most of them don't care about the cost of storage, they will just order more, it isn't their money.  Most of them don't want to spend any extra time configuring the swap storage.

What are the pros and cons of moving it to a local or shared SATA position?

You now have the VM spread out over multiple datastore.  (not sure that is a bad thing)
If it is on local only it will take longer to VMotion because it will have to recreate the vswp file (So what, it takes 60 seconds instead of 15 seconds and there is still no down time)
SATA and local are cheaper and it frees up your High performance expensive storage for something else.

I have only moved them to an alternate shared storage on one occasion.  One of my customer was trying to limit replication accross a WAN link while using VMware SRM, so we put all of the vswp files onto a Shared LUN that was not replicated to the DR site.  This did help with replication.  We also went into teh VM and created a D: drive and put the pagefile.sys onto the D drive which we stored on a non replicated LUN.

Hope that helps.