The 3-2-1 rule: backups that really save your data
Three copies, two media, one off site – and why a backup you have never restored is not a backup.
Saurus Group
A disk failure, ransomware, an accidentally deleted folder or a fire in the office – any of these can wipe out years of work in a second. The only reliable answer is backups made by the rule.
What 3-2-1 means
- 3 copies of the data – the original and two copies.
- 2 different media – for example a server and a NAS device, or a disk and cloud storage.
- 1 copy off site – in another data centre or the cloud, so the same event cannot hit it and the original.
The most common mistakes
- A copy on the same disk or server. When the server fails, the copy goes with it.
- A copy that is always connected. Ransomware encrypts it as well. At least one copy should be immutable or disconnected.
- A copy that is never checked. You do not know whether a backup you have never tried to restore actually works.
How we do it
Copies are made automatically every day, with checksum verification. From time to time we restore a copy to a separate environment and check that the data is readable. If you need a backup plan for your company’s servers or computers, see Web hosting and servers.
