2014
02.14

When enabling Hyper-V Replica for Windows VMs, it is recommended to move the guest OS paging file from the C: drive to another virtual hard disk. This allows you to deselect that paging file virtual hard disk from replication, thus saving needless bandwidth.

Microsoft has published a support article for when configuring a page file on a SCSI drive fails on Generation 1 Hyper-V virtual machine.

Symptoms

Consider the following scenario:

  • You create a virtual machine that is running on Windows Server 2008 R2 or Windows Server 2012 Hyper-V.
  • You manually configure a page file on a non-system drive, which is a virtual hard disk (VHD) attached to emulated SCSI adapter.
  • You restart the virtual machine.

In this scenario, no Pagefile.sys is created under the selected drive. Additionally, on Windows Server 2008 R2 Hyper-V, you receive the following error message

Windows created a temporary paging file on your computer because of a problem that occurred with your paging file configuration when you started your computer. The total paging file size for all disk drives may be somewhat larger than the size you specified.

Status

This behavior is by design.

In generation 1 virtual machines, you should create a virtual hard disk on the VM’s IDE controller and move the paging file to that new disk. There are no issues with the paging file being on a SCSI controller in generation 2 virtual machines; they don’t have IDE controllers.

3 comments so far

Add Your Comment
  1. Better yet, ignore all this extra work and provide enough memory to keep swapping, for sake of performance, to nearly zero. As long as perf.counter pagefile_usage_peak stays under 1% it doesn’t really matter you have the pagefile replicated aswell. Nearly zero changes to it means near zero overhead replicating it (Apart from the capacity taken once that is). I’ve found this to performance way better than less memory and much more swapping (quite logical).

  2. Maybe because the page file is created or verified before the scsi controller synthtic driver loads. And for Generation 2 VMs, no need for drivers for the scsi controller.

  3. Ah, thanks, I was puzzling on this. I swore I had done it in the past, but thought maybe there was some new restriction on pagefiles being on the boot drive, or some minimum.

Get Adobe Flash player