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Simplifying TrueNAS Replication with an External USB Drive

Don't believe what others tell you—using an external USB drive with TrueNAS is not only possible but also straightforward and beneficial. Forget about the complicated and slow "use software XY" suggestions. Here's a simpler, more efficient method.

Setting Up Your External USB Drive

  1. Attach the USB Drive: Connect your external USB drive to the TrueNAS system.
  2. Create a New Pool: In the TrueNAS web GUI, create a new pool and select the USB drive as the single disk.

Using TrueNAS Replication Task

TrueNAS' Replication Task function allows you to replicate ZFS datasets from your main filesystem to the external filesystem. The beauty of this method lies in its efficiency:

  • Snapshot-Based Replication: The replication is based on snapshots, meaning it only replicates data blocks that have changed. The first replication is a full transfer, but subsequent replications only copy updated blocks.
  • Speed: I replicate a 4TB data pool to an external disk in under 60 seconds daily. Larger changes take longer, but the process always saturates the sequential write speed of the external drive, which is 150-180 MB/s.

Benefits of ZFS

Using ZFS on your external drive offers several advantages:

  • Checksums: Ensure data validity.
  • Snapshots: Easily manage and revert to previous states.
  • Compression: Save space and improve performance.

Considerations

While this method is efficient, there are a few downsides:

  • Hot-Plugging: ZFS is not hot-pluggable. To remove or power off the external disk, you must export the pool via the GUI, similar to unmounting.
  • OS Compatibility: ZFS is not available on all operating systems. However, once exported, you can connect the disk to any computer that supports ZFS and import the pool to access your data.

Final Thoughts

Even with redundancy through a mirror, a backup is still necessary. For more on this, search "RAID is not a backup" in your preferred search engine.

By following these steps, you can efficiently and effectively use an external USB drive with TrueNAS for your data replication needs.

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Vincentde Koning

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