Disaster recovery (DR) handles region-level or catastrophic failures. Your entire data center is gone. What now?
RPO (Recovery Point Objective): How much data can you lose? hour of data? minute?
RTO (Recovery Time Objective): How quickly must you recover? hours? minutes?
Strategies: Backup and restore (cheap, slow). Pilot light (minimal standby). Warm standby (scaled-down duplicate). Hot standby (full duplicate, instant failover).