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We have a machine running Windows 2008 Enterprise with the Hyper-V Server role. The machine has 48 GB of RAM, and a RAID1 of just 74 GB.

The VMs are stored on a SAN.

My question is, does the Hyper-V host server itself need a big swap file for anything?

I know the recommended size of the swap file is at least 1.5 times the amount of physical memory installed, but this is more than the amount of physical disk space. I could store part of the swap file on the SAN but I'd rather not do that.

In theory, being just a VM host, the machine should be able to run without a swap file at all, but I have my doubts. Anyone with first hand experience on this?

andreialecu
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VMware ESX admins have to pay attention to host swap file sizes because you can overcommit on memory. With Hyper-V, you can't overcommit on memory - for example, you can't take a host with 16gb of ram and start up 8 guests with 4gb of ram each. There's pros and cons to that approach. In a nutshell, though, you're right in saying it shouldn't need a host file - as long as you don't run anything on the host other than Hyper-V guests. If you remote desktop in and run things, or if you run third party backup or antivirus software on the host, you should set up a page file just to be safe. I've seen instances where people RDP into the host and run a backup software console written in Java, for example, and it needs gigs of memory in order to start & run a restore operation.

Brent Ozar
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