I have an external drive attached to the Proxmox node
/dev/sdb1 on /mnt/timemachine type ext4 (rw,noatime,quota,usrquota,grpquota,stripe=8191,data=ordered)
quotes work directly on the host (repquota, edquota etc)
This partition is mounted in a CT with:
mp0: /mnt/timemachine,mp=/home,quota=1...