Windows 11 VM: Corrupt files when using write back cache

[tenstareri]

On some of our VMs we are trying to use disk setting cache to Write back because supposedly it gives better performance. However, this seems to have lead to getting corrupted files in Windows. Is it possible that there is a bug here or are we possibly doing something else wrong?

 

[SteveITS]

FWIW there was this poster with Linux VMs but I haven't noticed other reports here.

J

Post in thread 'Disk cache none...safe or not safe?'

Aug 14, 2025

I don't believe I've seen that comment yet, and obviously it's not in the docs. How prevalent was that? Any OS? I don't think we've run into it but I know we haven't been doing lots of migrations lately.

It was quite reproduceable in my production environment with Ceph migrations done every other week. Again, YMMV. All VMs are Linux with qemu-guest-agent installed.

Was only through trial-and-error, I found the cache policies that work for ZFS & Ceph and no more corruptions.

• jdancer

• 

What storage are you using?