SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/tech-raid-not-backup

Why is a mirrored RAID array not a backup?

RAID adds disk redundancy, but it is not an independent recovery copy.

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  1. It never stores files
  2. It only works offline
  3. It is not an independent copy ✔

Why: A mirror quickly copies normal writes, including mistaken deletions or encrypted files. It also remains exposed to controller faults, theft, and other failures affecting the whole system.

Huh, didn't know that: RAID mainly improves availability during certain disk failures.

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The mirror copied every mistake because it takes reflection seriously.
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References

Answer: It is not an independent copy. A mirror quickly copies normal writes, including mistaken deletions or encrypted files. It also remains exposed to controller faults, theft, and other failures affecting the whole system.

  1. TrueNAS ZFS Primer www.truenas.com/docs/references/zfsprimer
    RAID and disk redundancy are not substitutes for a reliable backup strategy.
    Checked 2026-10-10.

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