HyperV Host don't merge checkpoints resulting in Backup Software failing with error, file is being used by another process

Question

Good evening, I'm really fed up at this current point in time. I have a Hyper-V Host running 4 VM's

2 major servers, 1 being SQL server and 1 running reports for SQL server.

When my backup software trying to run (Altaro), it fails with an error that the checkpoint cannot be created. When I'm trying to take manual check point within the manager, the system keeps failing saying the avhdx file is being used by another process. So basically, it looks like the Hyper-V is not merging the virtual disks. When I reboot the Host, the VM all of a sudden merge the disks.

I had a crap start to 2025 as my virtual server failed completely just before the actual SQL job took the dB backup and because of this avhdx file issue and my physical disks are completely being eaten up by space because of the size the differencing disks are growing and lost 1 full days of work

Any help/ guidance will be appreciated. Perhaps some do's and don'ts regarding Hyper-V and best practices / life experiences?

Answer 1

Hi Etienne Schutte,

Thanks for your post. Please use the following steps to remove and merge checkpoints again and see if backup software will occur the same error. Removing or merging checkpoints in Hyper-V can be done through the Hyper-V Manager or using PowerShell commands. Here's a general guide on how to do it:

1. On your Windows machine, search for Hyper-V Manager and open it.
2. In the Hyper-V Manager, select the virtual machine that has the checkpoints you want to manage.
3. Manage Checkpoints:
   • To merge checkpoints, you can select the checkpoint you want to merge and choose the 'Delete Checkpoint' option. This will merge the checkpoint with the one below it.
     • To remove a checkpoint without merging, you can export the virtual machine to create a copy without the checkpoint, then import it back.

If there is no Delete Checkpoint option in Hyper-V Manager, you can merge checkpoints using PowerShell. 1. Right-click on the Start button and select "Windows PowerShell (Admin)".

1. Run Get-VM -VMName "VM Name" to list all virtual machines and identify the one you want to merge checkpoints for.
2. Run Get-VMCheckpoint -VMName "VM Name" to list all checkpoints for the virtual machine.
3. Run Remove-VMCheckpoint -VMName "VM Name" -Name "Checkpoint Name" to merge the checkpoint.

If you don't want the checkpoints to be created automatically, open Properties of the VM, select Checkpoints under Management and uncheck Use automatic checkpoints

Best Regards,

Ian Xue

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