Zfs storage with directory.

a zfs directory can be used for pve storage . for instance created a zpool named tank.
Code:
zfs create tank/bkup  -o mountpoint=/bkup
then just set up that directory in pve. I used gui to create, here is what /etc/pve/storage.cfg shows :
Code:
dir: bkup
        path /bkup
        content vztmpl,iso,backup
        maxfiles 4
        shared 0
if your root pool has space for backups substitute rpool for tank above.