Disaster Recovery in Action: Rebuilding After a RAID Failure
RAID is not a backup. It’s a phrase we repeat often, and a client learned why the hard way when a second disk failed in their array before the first had been replaced. They thought everything was gone. Thanks to a disaster-recovery plan we’d put in place months earlier, it wasn’t.
What RAID does and doesn’t protect against
RAID protects against hardware failure of a disk — keeping you running if one drive dies. It does nothing against accidental deletion, corruption, ransomware, or multiple simultaneous disk failures. Treating RAID as a backup is one of the most common and dangerous mistakes we see.
The incident
A drive had failed silently weeks earlier — no monitoring, no alert. The array was running degraded with no redundancy left. When a second drive went, the array failed completely and the server wouldn’t boot.
Why this wasn’t a catastrophe
Because the disaster-recovery plan had three things ready:
- Verified, off-site backups taken daily and regularly restore-tested
- A documented recovery runbook anyone on the team could follow
- Known recovery objectives, so everyone understood the expected timeline
The recovery
- Provisioned a replacement server and rebuilt the OS and stack from the runbook.
- Restored data from the most recent verified off-site backup.
- Validated the application and data integrity before going live.
- Brought the service back within hours — with a known, small amount of data loss matching the backup schedule.
The lessons
Two things saved this client: real off-site backups, and monitoring — the failure should never have gone unnoticed for weeks. RAID buys you resilience against a single disk dying. A tested disaster-recovery plan is what saves you when reality exceeds that.
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