Property ‘MaxInternalSize’ does not exist in class ‘Msvm_VirtualHardDiskSettingData’ – VHDX on Hyper-V

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Sometimes we can mount a VHDX that had its checkpoints saved on another location. When trying to boot the VM we will have a “Property ‘MaxInternalSize’ does not exist in class ‘Msvm_VirtualHardDiskSettingData’.”

This is because the disk properties has changed and the VM is linking the checkpoint back to its parent, making the chain corrupted.

To remediate this, we will use the Set-VHD powershell snippet

Set-VHD "D:\path\Disk_CHECK2.avhdx" -ParentPath "D:\path\Disk_CHECK1.avhdx"
Set-VHD "D:\path\Disk_CHECK1.avhdx" -ParentPath "D:\path\Disk.vhdx"

Here we are stitching the newest checkpoint (Disk_CHECK2) to (Disk_CHECK1); then Disk_CHECK1 to the main Disk.VHDX.

Now, its very likely that you will receive a mismatch error:

There exists ID mismatch between the differencing virtual hard disk and the parent disk.

For this we will use the –ignoreidmismatch command:

Set-VHD "D:\path\Disk_CHECK1.avhdx" -ParentPath "D:\path\Disk.vhdx" –ignoreidmismatch

And now you will have a booting VM again!

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