ELI5: What is the 3-2-1 Backup Rule?
Keep 3 copies of your homework, save them in 2 different places (like your backpack and your computer), and keep 1 copy at a friend’s house. That way, no single disaster can wipe out everything.
Definition
The 3-2-1 backup rule is a widely recognized best practice for data protection: maintain 3 copies of data (the original plus two backups), stored on 2 different media types (e.g., disk and tape), with at least 1 copy stored off-site. This strategy protects against hardware failure, site-level disasters, and ransomware attacks by ensuring that no single event can destroy all copies.
Key Details
- The “3” means original data plus two backup copies — not three backups
- The “2” means two different storage media types (e.g., SSD/HDD and tape or cloud), reducing simultaneous failure risk
- The “1” means one copy must be off-site (physical or cloud), protecting against facility-level disasters such as fire or flood
- Off-site copies defend against ransomware; air-gapped backups add additional protection
- RTO and RPO goals drive how frequently backups are taken and how quickly they can be restored
Connections
- Parent: disaster-recovery — the 3-2-1 rule is a foundational backup strategy in disaster recovery planning
- See also: recovery-point-objective-rpo
- See also: replication