Disaster Recovery in Cloud
Disaster recovery (DR) is about planning for the worst. Whether it's a hardware failure, natural disaster, or cyberattack, a solid DR plan ensures your business can recover quickly with minimal data loss.
Key DR Metrics
┌──────────────────────────────────────────────────────┐
│ RTO (Recovery Time Objective) │
│ ───────────────────────────── │
│ Maximum acceptable time to restore service │
│ "How fast do we need to be back up?" │
│ │
│ RPO (Recovery Point Objective) │
│ ───────────────────────────── │
│ Maximum acceptable data loss (measured in time) │
│ "How much data can we afford to lose?" │
│ │
│ Example: │
│ RTO = 4 hours, RPO = 1 hour │
│ → Must recover within 4 hours, losing max 1 hour │
│ of data │
└──────────────────────────────────────────────────────┘
DR Strategies
┌─────────────────────────────────────────────────────┐
│ Strategy │ RTO │ RPO │ Cost │
├──────────────────┼─────────┼─────────┼─────────────┤
│ Backup & │ Hours │ Hours │ Lowest │
│ Restore │ │ │ │
├──────────────────┼─────────┼─────────┼─────────────┤
│ Pilot Light │ 10s of │ Minutes│ Moderate │
│ │ mins │ │ │
├──────────────────┼─────────┼─────────┼─────────────┤
│ Warm Standby │ Minutes│ Seconds│ Higher │
│ │ │ │ │
├──────────────────┼─────────┼─────────┼─────────────┤
│ Multi-Site │ Near │ Near │ Highest │
│ Active-Active │ zero │ zero │ │
└──────────────────┴─────────┴─────────┴─────────────┘
Backup and Restore
The simplest DR strategy. Take regular backups (S3 snapshots, RDS automated backups) and restore them when disaster strikes. Good for non-critical workloads with lenient RTO/RPO requirements.
Pilot Light
Keep a minimal version of your environment running in another region. When disaster strikes, scale up quickly. Example: A warm database replica and pre-configured AMIs ready to launch EC2 instances.
Warm Standby
Run a scaled-down but fully functional copy of your environment in another region. Scale up during disasters. Provides faster recovery than Pilot Light.
Multi-Site Active-Active
Run full copies of your environment in multiple regions, serving production traffic simultaneously. Provides the best RTO and RPO but at the highest cost.
Testing Your DR Plan
A DR plan you haven't tested is just a document. Regularly simulate failures, practice failover procedures, and time your recovery. Use AWS Fault Injection Simulator for chaos engineering. Document lessons learned and improve continuously.