Hi,
I don't think there's a straightforward way. Proxmox VE backups are currently designed to be per-guest. You can mark certain volumes of the guest with backup=0
if you don't want them to be included in the backup.
If you are using Proxmox Backup Server, you can backup individual volumes with proxmox-backup-client
, but it's not tightly integrated in Proxmox VE then and you need to make sure the guest is stopped while doing that.
Otherwise, you'll need to do it manually, e.g. using qemu-img dd
.