Duplicate disk signature on non-existent disk / partmgr event 58

[cq]

I'm getting this in the System event log:

Source : partmgr
Event ID : 58
Description: Changing the disk signature of disk 3 because it is equal to the disk signature of disk 0.

This happens twice during a VSS backup of several virtual machines. The event is logged on the VM host, and the backup for one particular virtual machine fails.

Trouble is, I don't have a "Disk 3". Going in to Server Manager / Disk Management, I can see Disk 0 (the boot disk), Disk 1, Disk 2 and CD-ROM 0. This correctly reflects the actual disks in the server.

So why am I getting the error that Disk 3 has the same disk signature as disk 0? Is there a reference somewhere to this Disk 3 that is actually pointing to Disk 0 so they are one and the same?

Any pointers would be appreciated.

 

[cq]

I found the answer to this, posting here in case it helps anyone.

I mentioned that the error occurs on a VM host. During the VM guest backups, the host creates Volume Shadow Copies of the guests and it is at this point the phantom "Disk 3" is created.

Using diskpart (diskpart/select disk 0/detail disk) I could determine that two of the virtual guests had the same Disk ID as the host and it was this that was causing the error. Disk IDs are supposed to be unique but these were clones of a base O/S build, and cloning does not alter the Disk ID, hence multiple identical values.

Changing the Disk IDs of the guests to unique values has cleared up the problem.