A backup is a copy of data kept somewhere else. Somewhere the original problem cannot reach. A fire takes out the server room. A ransomware attack encrypts the file share. A developer drops the wrong table in production. The backup is the recovery path. Without it, the data is gone.

The 3-2-1 rule has guided backup strategy for years: three copies of data, on two different media types, with one copy stored offsite. Ransomware groups know this and target backup systems first. They delete snapshots and encrypt backup servers before deploying the ransomware. Immutable backups, stored on write-once media or in object storage with retention locks, resist that attack. The backup cannot be altered or deleted, even by an administrator. That is the modern answer to a modern threat.

Backup types

• Full — complete copy of all data, slow but simple to restore
• Incremental — only changes since the last backup, fast but restore chains are long
• Differential — changes since the last full backup, a middle ground
• Snapshot — point-in-time copy, often at the storage layer
• Continuous — every change replicated in near real time

A backup you have never tested is a hope, not a plan. Restore drills prove the copies work before the real incident forces the issue.