In the world of IT, there are two types of people: those who back up their data, and those who *will* back up their data after they suffer their first catastrophic loss. The core principle of recovery is the simple, yet effective, **3-2-1 Rule**.
What the 3-2-1 Rule Means
The rule is designed to protect against all common failure scenarios, from hardware failure to catastrophic events like fire or theft.
- **3 Copies of Your Data:** The primary data (live files) plus two backups.
- **2 Different Media Types:** Storing the backups on different media protects against a single hardware failure type (e.g., store one copy on a local NAS and the other on cloud storage).
- **1 Copy Off-site:** At least one copy must be physically separated from the location of the primary data, protecting against ransomware, fire, or flood.
Modern Compliance and Immutability
For modern threats like ransomware, the off-site copy must be **immutable** (meaning it cannot be encrypted or modified by the ransomware) or protected by versioning. This ensures that even if your live system and local backups are encrypted, your cloud copy remains clean and ready for recovery.
