Resize VHD Hyper V Server 2008 R2

Question

I have a Windows Server 2008 R2 with Hyper V installed.

One of the virtual machines is a 150GB dynamically expanding virtual hard disk (Windows). I would like to shrink this to 100GB, however I can't seem to achieve this.

What I have tried so far;

• opened disk management on guest machine and shrunk the HDD by 50GB, this is now displaying as 'unallocated' in the guest.
• ensured there are no snapshots of the guest OS
• defragmented the guest machine
• selected the guest machine in Hyper V and ran 'compact'

However whenever I inspect the disk in Hyper V it's still showing as 150GB, there's no change.

I have also tried the diskpart tool, using the following commands on the guest OS however same result;

select vdisk File=”I:\path\to\your.vhd”
attach vdisk readonly
compact vdisk
detach vdisk

Am I missing something?

Few questions;

I've read that it's not possible to shrink dynamically expanding virtual hard disks- is this true? If I simply delete the VM in Hyper V, where will the 150GB be reallocated to?

I'm unable to export the VM and create a new one as my host machine is very low on space.

Answer 1

According to this article;

The VHD virtual disk format doesn’t support shrinking..

I tried the exact same steps for a long time and never had any success. Best to recreate the virtual disk if possible, save some time.

Answer 2

You can shrink Dynamically expanding virtual hard disks. you've shrunk the volume in the guest already so from PowerShell try:

Resize-VHD –Path c:\BaseVHDX.vhdx –SizeBytes 1TB (1TB is just an example)

or

Resize-VHD –Path c:\BaseVHDX.vhdx –ToMinimumSize

if it is a .VHD then use .VHD instead of .VHDX