The 3-2-1 rule means: 3 copies of your data, on 2 different types of storage, with 1 copy off-site — so no single failure leaves you without data.
It’s the most widely used rule in the industry for a reason — it covers almost every data-loss scenario with simple, actionable logic.
Breaking down the rule
3 copies: the original plus two backups — a single copy is never enough. 2 storage types: e.g. a local drive and the cloud — so a failure specific to one technology doesn’t destroy both copies. 1 off-site: at least one copy away from your office, protecting against physical disaster.
Why it works
Every individual failure scenario (drive failure, theft, flooding, ransomware) is covered by at least one of the three copies — there’s no single point of failure that leaves you completely exposed.
- 3 copies: original + 2 backups
- 2 different storage types
- 1 copy stored off-site