A perennial problem with a Hyper-V VM failing to start

Question

I keep getting an error when starting a particular virtual machine on Hyper-V.

The error:

'VSERVER' failed to start.

Synthetic SCSI controller (Instance ID XXXXX): Failed to Power on with Error 'The chain of virtual hard disks is corrupted. There is a mismatch in the identifiers of the parent virtual hard disk and differencing disk'.

The problem is fixed via this command:

Set-VHD "C:\Path\to\Hyper-V\VSERVER.avhdx" -ParentPath "C:\Path\to\Hyper-V\VSERVER.vhdx" -ignoreidmismatch

...and the VM will start right up again.

But after a random #s of shutdowns, the "VSERVER failed to start" error will crop up again and I have to go thru this whole process over again.

How do I prevent this in the future?

The VM is Gen 2, checkpoints are disabled, all integration services offered, configuration version is 8.

Hyper-V Manager is version 10.0.17763.1, Windows Server 2019 version 1809 (OS build 17763.6054).

Windows Update is up to date.

Thanks!

Side note: I've noticed that if I shut down the VM from within the VM (i.e. at the cmd prompt), it so far hasn't caused this error. I think, I'm not 100% sure, only because I just noticed that the VM has restarted fine the past 2 or 3 times I've done it this way. However (and I can't say this happens all the time), if I use Shut Down from the Hyper-V manager, and try to restart, it appears to result in the error. I think. I don't want to keep experimenting this way in case the error is indicative of a more serious underlying issue and I end up REALLY breaking things.

Answer 1

Hello,

Thank you for posting in Q&A forum.

If your VM has checkpoints, these checkpoints can cause disk chain corruption for many reasons. Actually keeping checkpoints for a long time can also lead to inefficient way of performing disk I/O on Hyper-V VMs. I recommend that you keep checkpoints merged, when there are unnecessary checkpoints on Hyper-V VMs, there is a greater chance of virtual disk corruption.

For detailed steps on merging virtual disk files, please refer to the following link.

https://learn.microsoft.com/en-us/archive/technet-wiki/6257.manually-merge-avhd-to-vhd-in-hyper-v

I hope the information above is helpful.

Best regards

Zunhui

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