# 3-2-1 backup rule

> Three copies of your data, on two different media, one of them off-site — the floor under every 'we have backups' claim.

One copy is a hope, two copies on the same disk are one failure, and three copies in the same building are one fire. The rule exists to separate the failure modes: production plus two backups, different storage (not the same RAID), and one physically elsewhere — the cloud counts if it is genuinely elsewhere.

The rule says nothing about restores, which is where most backup strategies quietly fail: a backup you have never restored from is a hypothesis. The scheduled restore drill — pick a file, pick a server, put it back — is what turns the rule into a fact.

## Related terms

- https://dfieldsolutions.com/en/glossary/ransomware.md
- https://dfieldsolutions.com/en/glossary/incident-response.md
- https://dfieldsolutions.com/en/glossary/gdpr.md

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Source: https://dfieldsolutions.com/en/glossary/backup-3-2-1
DField Solutions — Dunakeszi, Hungary — dezso@dfieldsolutions.com
Booking: see https://dfieldsolutions.com/en/contact