Hyper-V nested virtualization volmgr repair mode differencing disk diagram

Question

I set up a training environment in Azure using a Windows Server 2022 virtual machine as a Hyper-V virtual machine. The server has 32GB of RAM and 8 vCPUs, so performance wasn't an issue. After deployment, I partitioned the primary drive by reducing the size of the C: drive and creating a separate 80GB E: drive to enable data deduplication. From that E: partition, I deployed five guest virtual machines using the different disk associated with the syspreped background image. Initially, everything looked very stable. I even deployed a group of 8 virtual machines for students, and everyone used it on Monday without any problems. Then, the next morning, things started to go wrong. Several nested virtual machines suddenly failed to boot and went straight into automatic recovery/repair mode. When reviewing the event logs on the Hyper-V server, I kept seeing warnings related to volmgr appearing. I thought perhaps the deployment process had been corrupted somehow, so on Tuesday afternoon, I rebuilt and republished the entire lab setup from scratch. Again, immediately after publishing everything, everything worked perfectly... until Wednesday morning when the same boot errors reappeared. What puzzles me is that the virtual machines only failed after the lab system was powered off overnight or restarted afterward. During the day they worked normally without any problems. Could Hyper-V checkpoints, data sanitization, disk diversion, or the shutdown process itself be damaging the VHDs in some way? Honestly, I'm running out of ideas because students keep reporting failed practice sessions every morning.

Answer 1

Hi **Rizky Susanto,**Has your issue been resolved yet? If it has, please consider accepting the answer as it helps others sharing the same problem benefit too. Thank you :)

Domic V.

Answer 2

Hi Rizky Susanto,

To stabilize your environment, you must separate active virtual machine workloads from general deduplication:

Disable Deduplication: Turn off the feature on your storage drive via Server Manager or by executing the Disable-DedupVolume command in PowerShell.

Rehydrate the Files: Run an unoptimization job to restore the virtual hard disks to their standard, uncompressed state.

Alternative (If Deduplication is Required): Back up your data, wipe the partition, and explicitly re-enable Data Deduplication using the Virtual Desktop Infrastructure (VDI) profile. This specific profile is engineered to handle the active disk locks of running virtual machines.

Hope this answer brought you some useful information. If it did, please hit “accept answer”. Should you have any questions, feel free to leave a comment

VPHAN