Merge differencing disks (AVHD/AVHDX) to boot Hyper-V machine

I have had a torrid time merging differencing disks (AVHD/AVHDX) to the original boot HyperV machine problem. These files occupy most of the space on the host machine causing all the virtual machines running on the host to go into a pause state.

It is imperative to take a backup of the virtual machine concerned before running the merge process. The steps provided below do not guarantee a successful merge of the AVHD/X to the VHD/X.

Please find below steps to resolve the problem at hand:

1. Select Hyper-V server in Hyper-V Manager
2. On left-hand side, select Inspect Disk
3. Browse to location of restored AVHD/AVHDX files
4. Select one of the AVHD/AVHDX files > OK
5. Record parent disk name
6. Repeat steps 2-5 for each AVHD/AVHDX file, and record their order (from newest to oldest)
   • Note: do not use timestamps to determine which files to merge, as this could lead to overwriting the incorrect parent file
7. Select Hyper-V server in Hyper-V Manager
8. On left-hand side, select Edit Disk
9. Next > Select newest AVHD/AVHDX file
10. Followed by Next > Select Merge
11. Next > To the parent virtual hard disk
12. Finish
13. Repeat steps 7-12 for each AVHD/AVHDX disk, until only the VHD/VHDX disk is left for the machine
14. Mount VHD/VHDX in new virtual machine in Hyper-V and boot

In order to merge the files using PowerShell, you can use the below steps:

1. Open PowerShell and run command to navigate to directory where AVHDX and VHDX files are located:
   • Note: if files are on different disk than C:, first change to correct disk with disk letter in PowerShell prompt:
     • <disk letter>:
     • For example, if data is located on drive D:, command would be:
       • D:
   • To change to correct directory:
     • cd <directory path where files are located>
2. Run following command on each AVHDX file:
   • Get-VHD .\<name of AVHDX file>.avhdx
3. Note name of parent AVHDX file from ParentPath entry in output
4. Repeat steps 2 and 3 until you have a list of all AVHDX files with their respective parent AVHDX files
5. Beginning from newest AVHDX file (only AVHDX file with no child file), run following command:
   • Merge-VHD -Path ‘<path to AVHDX>’ -DestinationPath ‘<path to parent AVHDX’
6. Repeat step 5 on each AVHDX, always starting with newest available file
7. Once all AVHDX files are consolidated, merge last AVHDX with main VHDX file:
   • Merge-VHD -Path ‘<path to AVHDX>’ -DestinationPath ‘<path to main VHDX disk’

As far as I am aware, the internet calls this a manual method to merge the AVHD/X into VHD/X. Feel free to drop a comment in the comment section below. Thank you 🙂