Disaster Recovery: How to Plan and Test

RPO (Recovery Point Objective): maximum acceptable data loss. RTO (Recovery Time Objective): maximum acceptable downtime. These values guide the entire DR strategy. Example: e-commerce system with RPO of 1 hour and RTO of 4 hours means hourly backups and ability to restore within 4 hours.

- **Backup and restore:** Simplest, highest RTO. Ideal for non-critical data. - **Pilot Light:** Minimal infrastructure in secondary region. Medium RTO. - **Multi-Site:** Complete infrastructure in two regions. Low RTO, high cost. - **Warm Standby:** Reduced infrastructure in secondary region, scalable. Balances cost and RTO.

For AWS, use S3 Cross-Region Replication for data, RDS Read Replicas for databases, and CloudFront for global distribution. Automate infrastructure with Terraform or CloudFormation to quickly recreate in another region.

Untested DR plan is a DR plan that doesn't work. Perform quarterly tests documenting: actual recovery time vs RTO, data recovered vs RPO, issues found, lessons learned. Start with backup restoration tests, evolve to full failover in staging environment.

Document: recovery steps, responsible contacts, system dependencies, restoration order. Keep document accessible outside main infrastructure (Git repository, offline storage). Define clear roles: who coordinates, who executes, who communicates. Test contacts periodically.

Disaster recovery is insurance you hope to use, but need to be ready when needed. Invest in planning, automation and regular testing. Companies that need help with DR can rely on specialized consulting.