WARN: running QEMU version does not support backup fleecing - continuing without

[herzkerl]

I've enabled backup fleecing for one of our hosts, but keep getting this error message.

Unfortunately I can't find anything about the minimum QEMU version needed.
Also, when I edit the machine settings and set the version to latest it keeps resetting to 5.1 for some Windows VMs.

 

[fiona]

Hi,
it's not about the machine version, but about the running QEMU binary. You can find the minimum required e.g. from the changelog:

pve-qemu-kvm (8.1.5-5) bookworm; urgency=medium

  * implement support for backup fleecing

 -- Proxmox Support Team <support@proxmox.com>  Thu, 11 Apr 2024 17:46:48 +0200

Make sure to shutdown+start the VM after installing a recent enough QEMU version, or use the Reboot button in the UI which does the same (reboot inside the guest is not enough). Alternatively, you can also live-migrate to an already updated node.

Windows is very prone to (virtual) hardware changes, so you should be careful before changing the machine version (e.g. have backups, test on a clone first). IIRC, you can't use latest for Windows, it needs to be pinned to a specific version.