Proxmox includes tools (i.e., pve-zsync, Storage Replication) to send snapshots of your virtual machines to another system using ZFS replication. Neither of these, however, back up the Proxmox system itself. This guide will configure your Proxmox host and TrueNAS SCALE server to periodically back up the root ZFS pool on your Proxmox host to your NAS.
These instructions will result in a backup of everything on your Proxmox root pool, including any virtual machines you have running on the default local-zfs storage. You can customize the snapshot task if this isn't the desired behavior.
You must have installed Proxmox Virtual Environment using ZFS. The pool layout (stripe, mirror, RAIDZn) doesn't matter, but it must be a ZFS pool. Your Proxmox must must also be set up to allow root login via SSH using public-key authentication. This guide was developed using TrueNAS SCALE 23.10.1. While the same basic procedure will work with TrueNAS CORE, or other versions of TrueNAS SCALE, some of the options may be in different places.
TrueNAS performs ZFS replication over a SSH connection. To set this up, in the TrueNAS web UI, go to Credentials -> Backup Credentials. Under SSH Connections, click Add. In the new window that pops up, enter:
If your Proxmox hosts are in a cluster, the authorized_keys file will be shared among them, so you'll only need to generate one private key. You'll still need to set up a SSH connection for each host, but rather than generating a new private key, just choose the first one from the drop-down.
Then click Save.
If you're configuring the second (or subsequent) host in a Proxmox cluster, the SSH key will already be present, so you can skip this step. If not, follow these steps:
Still in the TrueNAS web UI, under SSH Keypairs, click on the one you just created. In the window that comes up, copy the Public Key.
Then log in to your Proxmox host via SSH or its web console. Paste the public key into /root/.ssh/authorized_keys.
ZFS replication operates on snapshots. When TrueNAS is replicating to or from another TrueNAS system, it's able to directly manage snapshots on the remote system. With a non-TrueNAS system, however, it isn't, so you'll need to create and manage them on the Proxmox host itself. This guide uses zfSnap to do this.
Log into the shell on your Proxmox host and install zfSnap by running apt install zfsnap. Then create your first snapshot by running zfSnap -a 5d -r rpool. You can confirm the snapshots are present by running zfs list -t snapshot.
Next, set up a cron job to create these snapshots on a schedule, and to delete old snapshots once they're older than the lifespan you've given them. Run EDITOR=nano crontab -e to edit your crontab (if you like vi, you can omit the EDITOR=nano portion of this command). Enter:
58 * * * * /usr/sbin/zfSnap -d -a 5d -r rpool
Then save and exit the editor. This will run every hour at 58 minutes after the hour (so that they'll be present for the replication task that runs on the hour), creating a recursive snapshot of rpool with a lifespan of five days, and delete any snapshots that are older than that lifespan.
If you'd like to change any of these details, consult the zfSnap help (zfSnap --help) fore more information on its options.
Replication tasks on TrueNAS need an empty destination, which needs to be its own dataset. You can create one under Datasets in the TrueNAS web UI.
Still in the TrueNAS web UI, go to Data Protection, and under Replication Tasks, click Add. In the window that comes up, enter:
.*. This will replicate all snapshots on the Proxmox host.rpool.At the next screen, set your desired schedule. I'll be running this replication hourly.
Now it's time to make sure this works. You should be back at the Data Protection screen in the TrueNAS web UI, and should have a replication task with a State of "Pending." Click the Play button next to that task, and in the window that pops up, click Continue. If it doesn't return an error in a moment or two, you should be good to go.