Running Windows Server Backup, Disk X has the same disk identifiers as one or more disks connected to the system.

Question

We have been having an occasional problem on Windows Server 2019 VM running under Hyper-V 2019, during backups. From what I have been able to determine, the backup, running from Hyper-V, triggers the VM to create Shadow Copies of the disks to be backed up. This process always causes a series of messages to appear in the Event Logs, such as: Disk 6 has the same disk identifiers as one or more disks connected to the system. Go to Microsoft's support website (http://support.microsoft.com) and search for KB2983588 to resolve the issue. and The disk signature of disk 6 is equal to the disk signature of disk 0. The VM has 6 disks (VHD files) attached, which are Disk 0 through 5. So disk numbers > 5 are, I believe, related to the shadow copies of the disks. And, from what I've read, it is expected that these messages will appear, because the shadow copies have the same disk signatures as the original disks.
Where we have a problem is that sometimes, we see a message like this: The disk signature of disk 5 is equal to the disk signature of disk 10. In this case, the "real" disk appears first in the message, before the shadow copy disk. After that, the real disk is forced offline, which in turn causes all sorts of other problems, since it is effectively pulling the disk out of the VM and crashing whatever programs (i.e. SQL Server) depend on that disk. Has anyone else seen anything like this? Any ideas how we can prevent this from happening? Thanks in advance. Rick

Answer 1

I have seen similar issues with virtual machines with multiple VHDX files that may have been attached/transferred from other virtual machines before or copied and re-used. The easiest fix to that problem would be creating a similar virtual machine from scratch (including all the virtual disks) and migrating the data. A quicker option would be trivial cloning using Windows Admin Center or free V2V Converter https://www.starwindsoftware.com/starwind-v2v-converter.

Answer 2

Hi Rick,

Hope you're doing well.

1. Ensure that your VM's disk configuration is set up correctly. Verify that there are no conflicts in disk numbering or configuration within Hyper-V.
2. Make sure that your Windows Server 2019 VM and Hyper-V 2019 host are fully updated with the latest patches and updates from Microsoft. Sometimes, issues like this are addressed in software updates.
3. If the problem persists, you may need to intervene manually when such conflicts occur. This could involve temporarily detaching and reattaching disks to force Windows to assign new disk signatures. However, this should be done cautiously and preferably during maintenance windows to avoid disruptions.
4. In addition, you can use "diskpart" to check all disks' Uniqueid.

Best Regards,

Ian Xue

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