Snapshots protect against accidental deletion and corruption on the same pool, but they don’t protect against losing the entire NAS itself — a drive failure beyond your redundancy level, theft, or fire. TrueNAS Scale replication solves this by efficiently copying your ZFS snapshots to a second TrueNAS system, ideally located off-site, completing the off-site component of the 3-2-1 backup strategy specifically for your NAS data.

Why Replication Instead of Just Copying Files

ZFS replication sends the actual underlying snapshot data blocks rather than performing a traditional file-by-file copy, meaning subsequent replications after the first only transfer the data that’s actually changed since the last snapshot — dramatically more efficient than re-copying an entire dataset every time, especially relevant for off-site replication where bandwidth is often the limiting factor.

Replication Requirements

• A second TrueNAS system – ideally physically separate from your primary NAS, whether at a family member’s location, a colocated server, or even a second machine in your own home for at least some protection against single-drive failures (though real off-site placement matters more for disaster protection)
• Network connectivity between both systems – either a direct connection if both are on your own network, or a VPN connection if the destination is genuinely off-site
• Existing snapshot tasks – replication sends snapshots that already exist, so a periodic snapshot schedule needs to be configured first

Setting Up Periodic Snapshots (If Not Already Configured)

1. In TrueNAS Scale, go to Data Protection → Periodic Snapshot Tasks.
2. Click Add, selecting the dataset you want protected.
3. Configure a schedule (daily, hourly, or whatever cadence fits your actual data change rate) and retention period.

Setting Up SSH Connectivity Between Systems

Replication typically transfers over SSH, requiring key-based authentication (following the same principles as the SSH hardening guide covered earlier) configured between the source and destination TrueNAS systems:

1. On the destination system, note its SSH connection details.
2. On the source system, go to System Settings → SSH Connections, adding the destination system’s details and establishing key-based trust between them.

Creating a Replication Task

1. Go to Data Protection → Replication Tasks.
2. Click Add.
3. Select the Source dataset (on this system) and Destination (the dataset path on the remote system).
4. Choose which existing snapshot task to base replication on, or configure a naming schema matching your existing snapshots.
5. Set the replication schedule — often matching or slightly trailing your snapshot schedule, ensuring newly created snapshots get replicated promptly.

Understanding Incremental Replication

After the initial full replication (which transfers your complete existing dataset), subsequent replication runs are incremental, sending only the blocks that changed since the last successful replication — this is where ZFS replication’s efficiency truly shows, since ongoing off-site replication of even large datasets typically involves modest bandwidth once the initial full transfer is complete.

Replicating Over a VPN for real Off-Site Protection

For a destination system that’s really physically separate (not just a second machine on your same home network), route replication traffic through WireGuard or Tailscale , ensuring the connection between systems is both secure and doesn’t require exposing SSH or TrueNAS’s management interface directly to the public internet.

Monitoring Replication Status

TrueNAS Scale shows replication task status and history directly in the web interface, and can be configured to send notifications (via the SMTP relay setup ) if a replication task fails, ensuring you’re aware promptly rather than discovering a broken off-site backup only when you actually need to restore from it.

Testing Restores from Replicated Data

Following the same principle emphasized in the earlier 3-2-1 backup guide, periodically verify your replicated data is actually restorable — mounting a replicated snapshot on the destination system and confirming the data is intact and accessible, rather than assuming successful replication automatically means a successful eventual restore.

Replication vs Cloud Backup: Using Both

TrueNAS Scale replication to a second physical system and the Restic-to-cloud-storage approach covered in earlier guides aren’t mutually exclusive — many homelab users run both, using ZFS replication for a fast, complete NAS-level disaster recovery copy, while Restic’s encrypted, deduplicated cloud backups cover specific critical files with the additional redundancy of cloud storage geography entirely independent of any physical location you control.

Final Thoughts

Setting up TrueNAS Scale replication provides real, efficient off-site protection for your NAS data specifically, completing the physical redundancy layer that on-pool snapshots alone can’t provide. Combined with a properly secured connection (via VPN) to a particularly separate destination system, replication rounds out your NAS’s disaster recovery posture as a direct extension of the 3-2-1 backup principles covered earlier in this series.

Related Posts

• Running Apps Directly on TrueNAS Scale: A Practical Guide
• How to Set Up SMB and NFS Shares in TrueNAS Scale