Guide

The 3-2-1 backup rule, explained without the jargon

The 3-2-1 rule gets repeated constantly in backup advice, often without anyone explaining why those specific numbers were chosen.

Three copies

One working copy plus two backups means that losing any single copy still leaves two others standing. A single backup is better than none, but it is still just one failure away from zero.

Two kinds of storage

Keeping both backups on the same type of device means they share the same weaknesses — the same drive model, the same expected failure pattern. Splitting across a local drive and a different kind of storage removes that shared weak point.

One copy somewhere else

A local event — theft, fire, a spilled drink — can destroy every copy in the same room at once. Keeping one copy physically elsewhere, including in a cloud service, protects against exactly that scenario.

Questions people ask