I have stood up a 2008 R2 Server running only a Hyper-V role. The *.vhd files are stored on a separate partition. The files (including hidden files) within the C:\ drive consume about 12 GB of disk space. Yet, when I check the local disk, C:\, it says that I am using 73.4 GB of space. This was not the case before I configured the box to run the Hyper-V role.

So, my questions are:

  1. Where is this space being used if not within the directory structure?
  2. Is this directly attributable to Hyper-V?
  3. Will this space consumption grow as I add another .vhd?
  4. Are there other files besides the .vhd that need to be, or can be, stored outside of the system directory?

The goal here is to make sure we do not run out of space on the system drive as we anticipate adding 4-6 virtual machines in the immediate future.

Thanks for your help.

  • 1
    Have you checked your disk usage using a tool like WinDirStat or TreeSize? This would answer questions 1 and 2 which need to be answered before 3 can be answered. With regards to 4, you shouldn't mess with the location of system files. – squillman Oct 16 '13 at 14:03
  • Agree, he needs to run Treesize to see whats eating up the disk space. – Trondh Oct 16 '13 at 19:22

Did you count system files? Usually pagefile.sys grows to be at least the same size as the amount of RAM installed.

  • It appears that pagefile.sys is the culprit. I'll have to add more drive space to account for that. Thanks for the input. – user55390 Oct 16 '13 at 21:13
  • Windows is a little dumb when it comes to sizing the page file, especially on a Hyper-V host with a ton of memory. You can likely lower the size quite a bit. See here for some more info - blogs.technet.com/b/mghazai/archive/2011/05/26/… – Doug Luxem Oct 16 '13 at 21:38

Hyper-V VMs consist of the following: 1. vm "definitions" - small xml files 2. Hard disk files - vhd/vhdx files 3. Snapshots - can't remember the extension

You mentioned that vhds are already on a separate drive, could you check whether the snapshots (if used) might reside on C:? These might grow quite large.

  • .avhd is the snaptshot file extension. – DanBig Oct 16 '13 at 14:03
  • Thanks. I have not configured snapshots yet, as this box hasn't gone into production, so there are no *.avhd files located anywhere. Additionally, both the .xml and the .vhd are located on the separate partition. – user55390 Oct 16 '13 at 14:17
  • There is also a location for Smart Paging (usually C:\ProgramData\Microsoft\Windows\Hyper-V) and (some) space for logfiles. – Martijn Burger Oct 16 '13 at 14:44

You probably have the "Automatic Stop Action" for your VMs set to "Save the virtual machine state." When you have this chosen (and it's the default) then enough space is reserved for the VM's RAM so that you definitely can save it when the host machine shuts down or reboots. And, by default, the local for these files is with the VM configs on the c:.

For any guest OS for which you have the Integration Components installed, it's usually more appropriate to choose "Shut down the guest operating system" as the automatic stop option. At that point, your disk space will be reclaimed.

  • I changed this setting per your suggestion to "Shut Down the Guest OS", and rebooted, but I still have the same space allocation. Thanks for the suggestion though. – user55390 Oct 16 '13 at 20:46

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