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I am considering migrating from (debian + mirrored raid + daily differential backups + weekly full backups) to ZFS raidz. Is there any point of performing backups in ZFS the same way as my current setup? To my understanding snapshots provides full filesystem history and backups are only needed for more security. In case of emergency I allways keep weekly full backup on external drive.

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  • Why is RAID not a backup? on Server Fault is applicable. ZFS is not a panacea. Snapshots solve some of the situations where backups can help, but not all. But if you are happy with potentially losing a week's worth of data, then sure, what you propose may be good enough. It's all about time to recovery and to what point in time (in other words, how recent state you can restore to, and how quickly you can get there). What happens if the ZFS pool bombs out for some reason (lightning strike, say) while the weekly backup job is running?
    – user
    Nov 29, 2016 at 13:09

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There's a lot of questions here. How are you doing back ups now? To tape? To another local disk? Offsite?

ZFS works best (depending on your interpretation of "best") with mirrored pairs (i.e., striped mirrors, aka RAID 10), adding mirrored pairs to your zpool whenever you need more space. RAIDZ has some severe performance problems under some workloads.

If your back up strategy is just to copy to another local disk then just go with ZFS mirroring instead.

If your back up strategy is something else, do a zfs send after each snapshot.

If you're going to use Solaris 11 or OpenIndiana look into the zfs/auto-snapshot services (the feature that backends Time Slider). The auto-snapshot services support running an arbitrary command after each snap (thereby automating sending to tape or remote).

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  • Thank You. Can you specify "problems under some workloads"? I only know RAIDZ is 'best' with big files.
    – piotr
    Jul 20, 2012 at 10:18
  • RAIDZ may perform best on large files, but mirroring will probably still out perform it. Here's three articles which are all good reads on the topic: 1) 10 Ways to improve ZFS Performance 2) Why Mirroring is Best 3) ZFS Recomendations
    – bahamat
    Jul 20, 2012 at 16:49
  • Mirroring is not a backup. It protects against outright drive failure, but it does not protect against things like user error, software going on a killing spree deleting or overwriting files, or anything else that from the file system's point of view is any sort of intended usage. Depending on your physical setup, it might not even protect against controller malfunctions. Recognizing the limitations, mirroring can be a very powerful tool; relying on it for tasks for which it is not suitable will at some point be a very painful lesson. Snapshots + mirroring should be reasonably safe though.
    – user
    Dec 9, 2013 at 9:10
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If you schedule your snaps weekly, you will be fairly close to your previous setup. If you bomb out completely you will not recover any snapshots since your last weekly. I would recommend getting familiar with the zfs send/receive commands. Very powerful stuff. I send zfs streams all over the place: file, other zfs pools, other zfs hosts, cloud, etc. Love the zfs

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  • Thanks. So in daily snapshot routine, keeping last 14 I have 2 weeks file history safely backed up?
    – piotr
    Jul 20, 2012 at 10:25

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