Manually merge checkpoints if chain is broken

I had a situation when VM had 42 checkpoints after backup failure. I’ve tried the actions from my article Merge checkpoints (avhdx / vhdx), but it didn’t work, I had┬ácatastrofic failure error.┬áThat means the chain of snapshots (checkpoints) is broken.

Follow these steps to fix the issue:

  1. Turn off the VM and backup VM’s content
  2. Open Hyper-V Manager where is VM located. This will assures you have proper access permissions to the virtual disk
  3. Click on Edit disk, select the folder where VM keeps it’s vhdx
  4. Select very last check point file (with .avhdx extension)
  5. Select “Merge”
  6. You will be asked to confirm merge this file with the parent disk. The parent disk is a previous .avhdx file
  7. Do it until you have no avhdx files in VM’s folder. At the end you should have just single vhdx file
  8. Your VM will not run with this disk, because its only remember last avhdx file. Create new VM and copy vhdx file to there, attach it in VM’s hardware configuration.
  9. You will need to reconfigure network settings as well because your VM also get new vNIC.

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5 Comments

  1. I copied vhdx and avhdx files to test environment after powering off the virtual machine. after selecting latest avhdx file in hard drive setting(vm settings) i power on the VM in test environment. i am getting the error “The chain of virtual hard disk is inaccessible. There was an error opening a virtual hard disk further up the chain. When try to merge using edit disk wizard after selecting latest avhdx it is asking for reconnect to parent. then i selected parent. when i try to finish the wizard it is saying failed to set new parent. id mismatch … do you provide solution for this problem? live environment running on the file(which was a avhdx renamed to vhdx) do you provide solution for this problem?

  2. I stumbled across this while researching a similar problem. I have a Hype-V VM that has a single entry for a snapshot/checkpoint, and I am unable to delete it. I recently setup a new Hyper-V to act as a replica server. Unfortunately the other Hyper-V fails to replicate.

    I checked the virtual hard disk folder and discovered 57 .avdhx files, and the 1 .vhdx file. All of the dates on the .avhdx files are from last week until today (every time I attempted to initiate a replica).

    I’m assuming your steps above would work. I had a quick question. Step 4, you say select the “last” .avhdx file. I assume you mean the most recent which the Hyper-V is currently operating from? and then start merging with the .avhdx file that came before that, and so on until I get to the original .vhdx file?

    Thank you.

    1. Hi Philip!
      Thanks for comment!
      In “broken” state VM config know the location of avdhx file (because it replaced original vhdx file). As soon you merged all avdhx to single vhdx you need to create new VM config and attach vhdx file.

      Best regards,
      Dmitry

  3. Thank you for this. I found I did not have to create new VM though. I just edited the VM Removed the Disk and then added back the newly merged Disk.

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