Yeah, I’m kind of late to the party here. I’d played with PBS a little bit when it was in beta, and wasn’t able to get it working to where I saw the benefit, my Proxmox hosts were backing up to my TrueNAS box just fine, and Proxmox seemed pretty insistent that it run on its own bare-metal hardware, so…
After seeing some Youtube videos, I decided to give it another shot, this time installing as a VM, and using storage on my TrueNAS server. Installing in the VM was trivial; it’s just another VM on Proxmox. The remote storage was harder–Proxmox has their own idea of how PBS ought to be used, and while they don’t actively prevent, they also do nothing to facilitate, your using network storage.
I first tried to use an existing NFS export on my TrueNAS box, one which I was already using for other Proxmox-related stuff. I couldn’t get it working–it looked like permission-related problems, but I wasn’t able to resolve them.
But then, inspired by https://it.megocollector.com/linux/proxmox-backup-server-pbs-with-iscsi-resolved/, I decided to try iSCSI. I set up a 2TB iSCSI extent on my TrueNAS box, was able to connect it to the VM following the instructions at that link, but formatted it ext4 rather than ZFS (ZFS on ZFS isn’t generally recommended, and I didn’t see that it’d give any benefit in this case). Mounting that remote disk, then, was just a matter of a
/etc/fstab entry. Once that’s done, it acts like a local disk to the system, so setting it up as a datastore in PBS was straightforward.
Setting up the PVE host to back up to PBS is also quite straightforward–though if you’re planning on getting a Let’s Encrypt cert for your PBS system, do that first. Then add it as storage to the datacenter, and you’re ready to set up backups as desired.
But having done that, it’s fast. Doubtless this is because it uses incremental backups, while the “normal” backup to a NFS share doesn’t. But a backup of all the VMs on one of my hosts takes about 1/8 the time it did when going to the NFS share. Definite win there. Only limitation is that I can’t back up the PBS VM to itself, which I guess makes sense.
Now, I know the backup client is available separately and can be used on other systems; I haven’t messed with that yet. But that may be the next step.