[Bug Report] Hyper-V Server 2019 Command Line Tools access to the Volume Manager API [Repeatable Fault]

Question

I have found a bug in Hyper-V Server 2019. This may exist in Server Core 2019, but I've wasted my entire day on this already and do not care to try.

My Environment

• Hyper-V Server 2019 hosts, all identical
• Synology NAS running SMB 3, current DSM 6 release
• Dynamically Expanding VHDX files on a Synology SMB share - 3TB each. One formatted to ReFS, the other to NTFS
• A script is designed to mount the VHDX and Windows Server Backup operations occur on the VHDX

Went to run a one-off backup this morning to the ReFS disk and it wouldn't run. "ERROR - The specified backup location could not be found or is not a supported backup storage location."

Tried to create a NTFS formatted VHDX (assuming it was a ReFS issue) on the HV system, the hypervisors could create the VHDX, could online it, initialise it and create the partition, but could not format it.

Created the VHDX off-machine, moved it over, attempted the backup and it failed with the same error.

Fully patched the HV install to 2021-07, same error

Ran diskpart list disk - OK
Ran diskpart list partition - OK
Ran diskpart list volume - drive mount point (B:) not shown, volume missing

Go to cmd, can browse and search B:\ fine
Go to PowerShell can browser and search B:\ fine

Use Get-Disk, Get-Partition and Get-Volume in PowerShell - All OK, B drive is displayed as expected in PowerShell's WMI calls

Ran wbadmin get disks which can see the disk but gives:

Volumes: There are no volumes on the disk or Windows is unable to retrieve volume information.

Arduously De-installed the following KB's, rebooting after each

1. 5003258
2. 4494174
3. 4601558
4. 4589208
5. 4580422
6. 5003646
7. 5003171
8. 5001342

It all worked again after the removal of "2021-04 Cumulative Update for Windows Server 2019 for x64-based Systems (KB5001342)"

Installed "2021-03 Cumulative Update for Windows Server 2019 for x64-based Systems (KB5001638)" - all fine

Installed "2021-04 Cumulative Update Preview for Windows Server 2019 for x64-based Systems (KB5001384)" - broken again.

Roll back to 2021-03, all fine again.

It appears that something got into the 2021-04 branch and made it into production which has broken the API for reading the disk information. It is doing this on all of my Hyper-V Server 2019 installs. All of the installs work when rolled back to 2021-03.

All Windows Server 2019 GUI instances that I have are not exhibiting this issue.

A full and more comprehensive write-up can be found at: https://www.c-amie.co.uk/technical/hyper-v-server-2019-cannot-backup-to-or-format-a-vhdx-drive/

Anyone else seen this?

Answer 1

Hi,

Thank you for reporting bug to Q&A forum.

Actually, we have received some users' threads to report similar issues as you.

The issue occurs when attempting the backups to a Synology NAS device. At the moment, the workarounds can be summarized as below:

1. Backup to a windows-based network share.
2. Uninstalling KB5001347 if installed
3. Seek for assistance from support engineers of Synology

Also, we suggest that you could report the issue to Feedback Hub and contact Microsoft Customer Support and Services where more in-depth investigation can be done so that you could confirm with the developing team whether it is a bug and if there will be any fix for it.

You may find phone number for your region accordingly from the link below:
Global Customer Service phone numbers
https://support.microsoft.com/en-us/help/4051701/global-customer-service-phone-numbers

Similar threads for your reference:
https://learn.microsoft.com/en-us/answers/questions/362119/kb5001347-april-2021-update-issue-with-server-back.html
https://learn.microsoft.com/en-us/answers/questions/446762/windows-server-2016-hyperv-v-backup-error-340x8078.html

Thanks,

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