StarWind V2V Converter creates corrupt VHD/VHDX files on CSVs with 8KB allocation unit volumes

[rajdude]

StarWind V2V Version: 9.0.1.848 (also observed in 9.0.1.772)

Environment:

Source: VMware ESXi 7.0.3
Destination: Windows Server 2022 Hyper-V Cluster with CSV (Cluster Shared Volumes)
Storage: Pure Storage FlashArray presenting 20TB LUNs
Conversion Method: StarWind V2V GUI (Console/CLI not yet tested)

Issue Description:
StarWind V2V Converter successfully completes conversions but creates corrupt VHD/VHDX files when the destination CSV has an 8KB (8192 bytes) allocation unit size. The same VMs convert successfully to CSVs with 64KB (65536 bytes) allocation unit size.

Symptoms:
Conversion completes with "Converted successfully!" message
VHD/VHDX file is created on destination CSV
When attempting to start the VM or mount the VHD/VHDX:

Error: "The disk image isn't initialized, contains partitions that aren't recognizable, or contains volumes that haven't been assigned drive letters"
Error: "The process cannot access the file because it is being used by another process" (stale file handle from failed conversion)
Hyper-V cannot attach the disk to VM


Reproduction Steps:

Format destination CSV with 8KB allocation unit size (Windows default for 16-64TB volumes)
Use StarWind V2V GUI to convert VMware VM to this CSV
Conversion completes successfully
Attempt to start converted VM or mount VHD/VHDX
Result: Corruption errors

Workaround Confirmed:
Converting the same VM to a CSV with 64KB allocation unit size works perfectly:

No corruption
VM boots successfully
VHD/VHDX can be mounted and read

Questions:

Does StarWind V2V support 8KB allocation units?
Is 64KB the only supported allocation unit size?
Should this be documented in system requirements?

[CynthiaGutierrez]

No. StarWind V2V does not support 8 KB allocation units.

[yaroslav (staff)]

Thanks for sharing!
I doubt the provlem comes from StarWind V2V world as it takes the file system "as is" and redoes it to a new format.

[rajdude]

Thanks for the update. I find it interesting that StarWind does not support 8kb allocation units when it is the default allocation size from Microsoft. I am curious what the reason for that it. Now I need to move VMs off my new, six 20 TB CVS and format them with, ummm wait

What allocation size does StarWind V2V fully support?

I also have another interesting observation to share. After a lot of testing I have determined this:

StarWind V2V Version: 9.0.1.848 GUI makes corrupt files on CSVs formatted with 8kb allocation units (CLI of this version was not tested)

StarWind V2V Version: 9.0.1.772 GUI and CLI both do NOT make corrupt files on CSVs formatted with 8kb allocation units

[rajdude]

No. StarWind V2V does not support 8 KB allocation units.

I searched through StarWind documentation but could not find any details on what they support. So, before I embark on re-formatting my CSVs, I am wondering if this answer is definitive?

CynthiaGutierrez, with all due respect, I see you are a new user at this time (just one post). Are you StarWind staff or a user who has experienced the same problem as me?

[yaroslav (staff)]

I will log a case with R&D.