I have two external USB drives that I rotate to an offsite location. Both formatted as zfs, and using replication to update the backups. But over the last few days I’ve come across a couple of threads on external backups where ext4 is used/recommended. Is there any downsides to zfs/upsides for ext…

In addition to the other comments, I would add these as benefits for ZFS: Built in compression Ability to use copies=2 for some datasets for that extra reliability Snapshots for backup history Bad block recovery, (from other source) Built in encryption For the last, Linux does support whole disk …

ZFS can be scrubbed and is checksummed in ways that ext4 dreams of. Plus, it can be used as a sneakernet replication that also allows you to go forward and backward in time, which can be super useful re ransomware. Ext4 will only be whatever the latest version was when the backup was taken. But it …

Thanks! Those are the benefits I have in mind as well, for both zfs and ext4. The ones for zfs is more important to me, so I’ll stay with that then. :slight_smile:

You can even mount the drives on a Mac if necessary.

[image] Arwen: Bad block recovery, (from other source) This is one of those half complete features that the devs didn’t bother finishing properly. [image] Arwen: Ability to use copies=2 for some datasets for that extra reliability Give me one good reason I shouldn’t add you to my i…

[image] Arwen: In regards to snapshots on the backup disks. A common method for backups is ZFS Send & Receive and replicates the source to the destination. Is that what happens when one configure a Replication task in the GUI?

Yes. The low level term is ZFS Send & Receive, which existed years before FreeNAS or TrueNAS and it’s GUI.

Thanks! Will dig into the config options! :slight_smile:

ZFS is undoubtfuly better than ext4 due to all these features that are mentioned here. However, the full power of zfs features manifest in the set of multiple hard drives (the more drives, the better)! Only in this case, one can benefit from the most reliable file system. Now, pay attention to the …

Exactly. Have both zfs and ext4 USB drives for extra backups. Came to the conclusion that I dont need all the snapshots or features, so Im currently testing ext4 with rsync and saving deleted files to a directory. If TN had execute-command-before it takes a snapshot, or replication, I would almos…

Zfs vs ext4 for external backups

TrueNAS General

winnielinnie August 4, 2025, 10:35pm 6

This is one of those half complete features that the devs didn’t bother finishing properly.

Give me one good reason I shouldn’t add you to my ignore list?

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Zfs vs ext4 for external backups

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