Following the instructions documented here, I have passed through a number of discs on my Xcp-ng host to TrueNas Scale in a VM.
I wish to backup the VM’s boot disk, which is an Xcp-ng volume in a storage pool. But I can’t.
I acknowledge that this is known behaviour. But is there any way to avoid it?
Just keep up to date with your Truenas backups - including encryption keys for the storage pool (if configured)
In the event of failure of the boot drives, reinstall and restore the backup.
If you have enough space, mirror the boot drives.
There is a discussion on this topic in their forums
I second this. I use the nobak for some drives.