I have a Windows Sever 2012 Standard 64-bit running Hyper-V. The Hyper-V is hosting a guest OS of Windows 7 Professional 32-bit. I noticed that I was running out of disk space on my server. So I uninstalled a bunch of unneeded software. I rebooted the guest machine, and the server. After that I powered off the guest machine and I compacted the virtual disk drive that the Windows 7 system uses.

Even though I have removed 16 GB from the guest system, the used space on the physical server hard disk, is still showing that there hasn't been any change to the size of the virtual disk on the physical sever.

Windows 7

Windows Server

Can some please tell me how I can reduce the size of my virtual disk on my physical servers hard disk?

I have also made a video here that describes my issues, with the updated answers and comments from the users here.

  • Did you run a defrag before compacting the disk?
    – Rex
    Apr 9, 2014 at 17:01
  • Maybe empty space isn't really empty space, just no longer allocated? I wonder if you have to do a zero-fill on hyper-v.
    – Zoredache
    Apr 10, 2014 at 0:13
  • @Zoredache Can you please be a little more descriptive?
    – nate
    Apr 11, 2014 at 16:21
  • @Rex I ran defrag, and tried to compact and shrink again. nothing has changed.
    – nate
    Apr 11, 2014 at 16:22
  • I mean if you delete a file, the blocks on the hard disk still contain the contents of the file. A deletion only changes the the filesystem metadata. For zero fill see: serverfault.com/questions/165070/…
    – Zoredache
    Apr 11, 2014 at 18:55

1 Answer 1


Convert the disk type to a "dynamically expanding" disk. (The more common term, which comes from the VMware world, is thin-provisioned disk). Looks like there's a walk through with screenshots on this Technet blog.

And, of course, as a best practice, this is why you have a separate system partition on your servers, and just use it for the operating system (and maybe an app or two), but store your data (in this case, guest VHDs) on a different partition.

  • Thank you for you response. I will convert them to dynamic, and see if that fixes the issue. I used the fix size so I could stop them going over 120 GB of space. Maybe what wasn't the best course of action.
    – nate
    Apr 9, 2014 at 16:55
  • Given that his vhdx file is showing as 80GB and the drive on the guest is showing a total capacity of 120GB, I would assume he is already using a dynamic/thin provision disk..
    – Rex
    Apr 9, 2014 at 16:56
  • I tried converting the disk to dynamic, I also converted from .vhd to .vhdx now the size on the disk is bigger by 270 MB
    – nate
    Apr 9, 2014 at 19:05
  • @nate Did you try compacting the disk as well? Apr 9, 2014 at 19:10
  • I didn't. I am doing that now
    – nate
    Apr 9, 2014 at 19:14

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