The 3-2-1 Backup Method

Three copies is an industry convention, not a guarantee.

Keep the working data plus two recoverable copies. Copies that share one device, account, or deletion path may fail together and should not be counted as independent.

Two media types and one offsite copy reduce common-mode loss.

A local external drive covers fast recovery; an offsite or isolated copy covers theft, fire, and some ransomware paths. Choose risks explicitly.

Synchronization can propagate deletion or corruption.

A service counts as backup only when it preserves recoverable versions or snapshots under the failure you are planning for. Verify retention and recovery rules.

An untested backup is only a hopeful copy.

Schedule small restore drills, record encryption credentials safely, and keep at least one offline or otherwise protected copy as recommended in ransomware guidance.