The 3-2-1 backup rule.
Three copies, two kinds of storage, one kept somewhere else. A simple rule that covers most of the ways data is lost.
Data is lost in ordinary ways: a laptop is stolen, a drive fails, someone deletes the wrong folder, ransomware encrypts the server. The 3-2-1 rule is a simple way to make sure that no single one of those can take everything.
The rule
- 3 copies of your important files: the one you work on, and two backups.
- 2 different kinds of storage, such as a drive in the office and a cloud service.
- 1 copy off site, away from the building the others are in.
Why each number is there
Three copies, because backups fail too, and usually without telling anyone. Two kinds of storage, because whatever damages one drive, such as a power surge or a faulty batch, tends to damage the one beside it. One copy somewhere else, because fire, flood and theft take everything in the room.
What it looks like in a small office
- Working files live in Microsoft 365, Google Workspace or on an office server.
- A backup service copies them every night to a separate cloud account.
- A second copy goes to a drive in the office that is disconnected when the backup finishes, or to storage that cannot be altered.
The copy that is disconnected or locked matters most against ransomware, which looks for backups it can reach and encrypts them too.
The step people skip
A backup that has never been restored is a hope, not a plan. Restore a file every month and check that it opens. The longer version is in A backup you have never restored is a guess.