I was recently asked to look at a server where staff would often lose access to network resources.
Wasn’t too difficult to track down, the resources were on virtual machines, the host was low on disk space so it was pausing them.
The long term fix would be to add some more storage but since there were plans to replace this host, a short term fix was needed.
So I found a couple of virtual hard disks were setup as dynamic. I figured since disk space was at a premium allowing them to expand on their own wasn’t great so getting them converted to fixed would be my first port of call.
The problem I had was there wasn’t enough free space for me to write the new VHDX file. There was a USB drive attached so while it wasn’t ideal and wouldn’t be quick I figured I’d write the new file to the USB disk. then delete the old dynamic disk and copy the new fixed disk in it’s place.
Obviously I took a backup first.
I fell over at the first hurdle though because as soon I started the wizard I got this error.
“Failed to convert the virtual disk”
Not a particularly helpful message so off to the event logs I went where I found this
“The locale specific resource for the desired message is not present”
Again not hugely helpful.
There was also this error number “0x80070299”
A very quick search gave me something much more useful. That error means,
“The requested operation could not be completed due to a file system limitation”
At that point I took a closer look at the USB drive and spotted the problem. It had been formatted as exFAT.
This Hyper-V troubleshooting document makes it very specific
When I try to create a virtual hard disk on a flash drive, an error message is displayed
Hyper-V does not support FAT/FAT32 formatted disk drives since these file systems do not provide access control lists (ACLs) and do not support files larger than 4GB. ExFAT formatted disks only provide limited ACL functionality and are therefore also not supported for security reasons. The error message displayed in PowerShell is “The system failed to create ‘[path to VHD]’: The requested operation could not be completed due to a file system limitation (0x80070299).”
Use a NTFS formatted drive instead
A quick format of the disk meant I was able to carry on.
Little frustrating that the error message initially display was next to useless but sharing this in case anyone else hits the same problem.