The 3-2-1 rule: back up without losing your weekends

Everyone knows someone who lost ten years of photos because a drive gave out. The 3-2-1 rule is the simplest defence to remember.

The principle

• 3 copies of your data: the original plus two backups.
• 2 different media: for example the PC's disk and an external drive, so you do not depend on a single technology.
• 1 off-site copy: in the cloud or at a relative's, to survive a fire, a burglary or water damage.

A realistic setup

1. On Windows, turn on File History to an external drive. The backup guide details the procedure and the robocopy command.
2. On Mac, plug in a drive and turn on Time Machine, with encryption: see the Time Machine guide.
3. On Linux, use a restore-point tool like Timeshift for the system, and a synchronisation tool for your documents.
4. Off-site: an encrypted cloud backup, or a second drive you leave with someone you trust and swap every quarter.

Classic pitfalls

• Synchronisation is not a backup. If you delete a file or a virus encrypts it, the synchronised copy is deleted or encrypted too.
• A backup that has never been tested does not exist. Once a quarter, restore a random file to check.
• Encryption. Encrypt backup drives and keep the key separately.

How long does it take?

Half an hour to set everything up, then almost nothing. It is the best IT investment of the year.