Compacting virtual hard disks

Compressing a vhdx file in Hyper-V

Well I have had fun today trying to compress some vhdx files used in Hyper-V.

My VHDXs only had around 15GB of files (10 pro Insider 15061) including hidden files after disk cleanup when in Hyper-V but the vhdx files were around 40 GB/

Tried following

1) to compact it using Hyper-V compact - no change

2) mounted vhdx as drive in host and used vdisk compact - no change

3) backed up vhdx using Macrium Reflect, deleted partition and restored - no change.

4) shrunk c drive to minimum size with partition wizard - no change

5) shrunk c drive to minimum size and expanded to full size with partition wizard - no change

6) backed up c partition from 5 above (deleting c partition in vhd in Macrium) and restored with Macrium - no change


So I did this then

7) deleted c drive partition in vhdx from disk management, and then restored c drive using Macrium (said full copying)- no change!

8) So I then created a new vhdx and restored the image backup to new vhd (Hoooray - file now only 15 GB)

9) renamed old vhdx with .bak and renamed new one to old name and ran hyper-v - would not boot.

Back to trusty Macrium - booted from Rescue Drive and used "fix windows boot problems" - SUCCESS!

So sequence is

a) mount vhdx in hyper-v, use disk cleanup etc.

b) mount vhdx in host disk management

c) shrink c drive to minimum, the re-expand to full size using minitool partition wizard or similar

d) image backup vhdx using Macrium Reflect

e) create new vhdx

f) restore image backup from Macrium Reflect to new one (renaming old to .bak and new name to old name).

g) repair boot files using Macrium in hyper-v if needed.

In hindsight, not sure if step c is needed. More testing needed.

Sounds like a fun trip indeed! I'll give that a shot with VMware Fusion VM too. Keep you posted.

Cheers

M4v3r1ck said:

Sounds like a fun trip indeed! I'll give that a shot with VMware Fusion VM too. Keep you posted.

Cheers

Never had a problem compressing vhds when I used VMWARE. Issue seems to be with vhdx files.

lx07 said:

I do this inside the VM before compacting - Defrag to consolidate free space then use sdelete to zero.

It works much better than just compacting the vhdx.

Code:

        {    $Command = "C:\Windows\System32\defrag.exe"
            $Parms = "C: /h /x"
            $Prms = $Parms.Split(" ")
            & "$Command" $Prms

            $Command = "C:\Windows\System32\defrag.exe"
            $Parms = "C: /h /o"
            $Prms = $Parms.Split(" ")
            & "$Command" $Prms

            $Command = "C:\Users\Hali\OneDrive\Programs\SysinternalsSuite\sdelete.exe"
            $Parms = "C: /z"
            $Prms = $Parms.Split(" ")
            & "$Command" $Prms
        }

Probably the save restore route with Macrium would be just as good (or better) but it is sometimes easier to run a script I think...

I always avoid defrag as it usually takes so long. Minitool does the same in effect in a fraction of the time.

What does sdelete do?

Edit: I have just seen this

Compacting Client Hyper-V VHDX Files • Helge Klein

cereberus said:

In hindsight, not sure if step c is needed. More testing needed.

Please do not take this wrong, I just have to say that your process involves awfully lot unnecessary work!

To start with, a dynamically expanding VHD can only grow. It never shrinks, that's not what Compact Disk means. Each checkpoint, even when later removed makes VHD bigger, and so on.

My workflow when I want to free unnecessary space used by my dynamical VHDs:

• Disk clean-up
• Create Macrium image of my VM
• Shut down VM
• Replace existing VHD with new dynamically expanding one in VM settings
• Restore Macrium image to new VHD

Can't understand why you mount VHD in host, can't understand why to save old VHD as .bak when Macrium Image exists.

Of course I also export all new Hyper-V virtual machines as soon as I have finished installing Windows, when the VHD file size is smallest. If then later I want to start from scratch, from freshly installed Windows, I just delete the VM and import it back.

Kari

op

Kari said:

Please do not take this wrong, I just have to say that your process involves awfully lot unnecessary work!

To start with, a dynamically expanding VHD can only grow. It never shrinks, that's not what Compact Disk means. Each checkpoint, even when later removed makes VHD bigger, and so on.

My workflow when I want to free unnecessary space used by my dynamical VHDs:

• Disk clean-up
• Create Macrium image of my VM
• Shut down VM
• Replace existing VHD with new dynamically expanding one in VM settings
• Restore Macrium image to new VHD

Can't understand why you mount VHD in host, can't understand why to save old VHD as .bak when Macrium Image exists.

Of course I also export all new Hyper-V virtual machines as soon as I have finished installing Windows, when the VHD file size is smallest. If then later I want to start from scratch, from freshly installed Windows, I just delete the VM and import it back.

Kari

Re. .bak - just cautious - I delete after I verify new vhd works.

What I found was that exporting vhdx using mrf alone and reimporting to new vhdx did not shrink the vhdx to minimum size possible. The minitool step does that (basically a defrag).

Sure you can do this inside vm - just found it faster doing in host.

cereberus said:

What I found was that exporting vhdx using mrf alone and reimporting to new vhdx did not shrink the vhdx to minimum size possible. The minitool step does that (basically a defrag).

We must have totally different working methods :)

Let's see what I told to be my workflow, and check how that works in reality. Example W10 x64 VM is one I have used for ESDtoISO and UUPtoISO testing, a clean installed build 15048 with no additional software installed, upgraded several times to builds 15055, 15058, 15060 and 15061, always restored back to clean 15048. This has of course caused the VHD size to grow to multiple times what really is needed.

Kari said:

• Disk clean-up
• Create Macrium image of my VM

After the above, checking file sizes. Macrium image was made when the original 64 GB dynamically expanding VHD was 34.5 GB:

Macrium image size just under 5 GB:

Kari said:

• Shut down VM
• Replace existing VHD with new dynamically expanding one in VM settings
• Restore Macrium image to new VHD

After restoring Macrium image to a new dynamically expanding VHD, file size is 9.3 GB. Over two thirds smaller than original one:

The same as seen by File Explorer, yellow highlight is the original VHD, start situation, and green highlight the new VHD where Macrium image from old VHD was restored. Old VHD can now be deleted, net storage save savings over 25 GB in this example case:

(Notice that VHD has already grown over 0.5 GB since the previous screenshot a few minutes earlier. This is because in previous screenshot VM was not started yet after restoring the image.)

This of course is all logical, happens every time.

Kari