Hyper V AVHDX will not boot after host os reinstall

Question

I had some issues with the host OS, therefore I have reinstalled it. Hyper V was hosting a machine with a Windows 10 on it.

After the server reinstall the AVHDX (I have a checkpoint which works but it is too old to run it from there) can no longer be booted.

The error is

Failed to power on with error The device is not ready

I tried both importing the machine and creating a new one using the AVHDX as boot drive but both fail the same way.

I tried to merge the images but when opening it I get some other error.

System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.Virtualization.Client.Wizards.EditVhd.ActionPage.SetPageLayout(VirtualHardDiskSettingData selectedDisk, VirtualHardDiskState selectedDiskState, Boolean reconnect)
at Microsoft.Virtualization.Client.Wizards.EditVhd.NamePage.FailureRetrievingSelectedVirtualDisk(VirtualHardDiskSettingData diskSettingData, VirtualHardDiskState diskState, Exception exception)

I tried to hit continue, I get a loading cursor but it stays like that for hours and it is not doing anything.

Answer 1

I was able to fix it with the following steps:

• Moved both AVHDX and VHDX images to Win Server 2016
• Opened AVHDX and relinked it from the Hyper V manager
• Created a new instance with the VHDX as main drive (since AVHDX cannot be added at this step) !!! important: do not start it !!!
• Edit the machine drive and replace the VHDX with the AVHDX
• Boot the machine - no errors or warnings at this point

Conclusions:

• Reinstalling Win 2019 Srv with the same settings might break things up
• The image editor of Win 2019 Srv has some issue given the errors presented at first (not related to the image itself)