Effective backup follows the 3-2-1 pattern: multiple copies, on different media or platforms, with at least one isolated from the system it protects. Modern threats make isolation and testability the critical properties — an online backup reachable by the same compromised credentials is not a recovery option; it is another target.
Key points
Isolated copiesOffline, immutable, or separately authenticated copies survive ransomware and credential compromise that reach everything else.
Restore testingA completed backup job proves data was copied; only a timed restore test proves it can come back within the RTO and RPO.
Important limitationBackups preserve data, not working systems — restoring operations also needs configurations, secrets, dependencies, and clean environments. A backup that silently failed or captured already-corrupted data protects nothing.