RAID is not a backup: the 3-2-1 rule, honestly — Homelab the Right Way
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What actually counts as a copy under the 3-2-1 rule, why a RAID mirror or a snapshot only protects against one kind of failure, and the one-page inventory that exposes the gaps.

What actually counts as a copy under the 3-2-1 rule, why a RAID mirror or a snapshot only protects against one kind of failure, and the one-page inventory that exposes the gaps.

  • wr2623@midwest.socialEnglish
    1·
    18 days ago

    I hate this take, and it seems to contradict itself.

    What actually counts A copy counts when it survives the loss of the thing it was copied from. That one sentence settles most arguments about what is and isn’t a backup.

    So doesn’t raid count then? If a drive fails and the second drive survives the loss, it is a backup…

    Just because the copy is synchronous doesn’t mean it isn’t a backup, it just means it protects from a different type of failure.

    • RAID: protects against a drive failure
    • Snapshot: protects against user failure (rm *)
    • Replication: protects against admin failure (zpool destroy)
    • Offsite tape/async backup: protects against replication corruption, and total site failure

    These are all backups, just with different recovery point objectives/recovery time objectives, and all just as important.