Hyper-V Disk merge fails

Senad Sadikovic 176 Reputation points
2021-05-24T12:52:19.29+00:00

Hi,

I'm having issues with a couple of VM:s in a customers Hyper-V environment. It seems that these 2 VM:s fail to merge the disks after the daily backup so a bunch of AVHDX files have been accumulating and eating diskspace on the host. I can see that "Date Modified" of the AVHDX files is from the same time the scheduled backup is supposed to run and it has been accumulating for some time.

There is also a Hyper-V replication running but it stopped itself later since the disk had insufficient space left. I shut one of the VM's down and started it again and then it actually started merging and succeded so i got alot of space left again, but looking at the event log i can see that the problem still persists with recurring merge failures.

I cannot see any checkpoints in the GUIor the powershell view.

This is what i see in Event Log on the primary Hyper-V host:

99040-merge.png

I tried rebuilding the replication of one of the servers since i suspected that it could be the problem but the initial replication just started filling up disks like crazy so i had to abort it. Does anyone have a clue what the problem is here and how it can be solved?

System Center Virtual Machine Manager
Hyper-V
Hyper-V
A Windows technology providing a hypervisor-based virtualization solution enabling customers to consolidate workloads onto a single server.
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Accepted answer
  1. Yuhan Deng 3,781 Reputation points Microsoft Vendor
    2021-05-25T02:51:09.92+00:00

    Hi,
    To deal with those avhdx files, you can try manually merging them:
    https://www.nakivo.com/hyper-v-backup/merge-hyper-v-snapshots-step-step-guide/
    Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.

    And for the error message, I would suggest that you restart the VMMS service fisrt, if the problem still exists, try this:
    https://www.makeuseof.com/fix-the-windows-access-denied-error-0x80070005/
    Please note: Information posted in the given link is hosted by a third party. Microsoft does not guarantee the accuracy and effectiveness of information.

    Thanks for your time.
    Best regards,
    Danny

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  1. Senad Sadikovic 176 Reputation points
    2021-05-26T11:19:20.187+00:00

    Hi, i restarted the VMMS service and the error has stopped re-appearing for one of the VM:s but the other one still logs those errors.

    Checked the disk status in Hyper-V for both VM:s and the problem was still there.

    Tried the icacls method by giving SYSTEM account full rights to the troubling vdx:s and it seemed to work, the disks merged without any intervention with restart or anything.

    icacls "full-path-to-vhd-or-vhdx-file" /grant "NT VIRTUAL MACHINE\Virtual-Machine-ID":(F)
    

    Next step is to observe the behaviour after tonights backup and then activate the replication once again and see if it keeps up the good work.

    If the merge hasn't started, you can restart the VMMS service and it will trigger that for you.


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