Lessons Learned From Running Disaster Recovery Drills

Disaster recovery (DR) is not just about backing up data — it’s also about ensuring that when the unexpected issue strikes, systems, people, and processes can recover quickly and efficiently. While planning and documentation are essential, the true test of a DR strategy comes from running drills. 

Through multiple exercises across organizations, here are the critical learnings that can significantly improve the effectiveness of DR initiatives.

1. Documentation Is Not Enough

Even the most detailed runbook fails when the issue occurs. As applications evolve, documentation becomes obsolete. The on-call team finds missing details that were not caught before. It will slow down the recovery process under pressure.

Key takeaway: Version control disaster recovery docs, and keep them close to the application code so that documentation is updated as the application continues to evolve. Regularly practicing disaster recovery procedures reveals gaps in documentation that must be updated.

2. Dependencies Are More Complex Than Expected

In a microservices architecture, applications have many dependencies that are only expected to grow with time. During disaster recovery drills, teams often discover new dependencies that were unknown.

Key takeaway: Maintain a dependency graph across services. Any untested dependency increases the recovery risk.

3. Communication Is a Technical Dependency

When an outage occurs, it not only impacts the system but can also affect processes that rely on communication channels. Chat tools, ticketing system, and video conferencing system will all depend on the infrastructure that is down.

Key takeaway: Always keep a backup channel for communication so teams can communicate when the primary channel is down.

4. Automation Speeds Up Recovery Process

The manual disaster recovery process is not only slow but error-prone. Investing in disaster recovery tooling reduces the risk and speeds up the recovery process.

Key takeaway: Identify repeatable processes that can be automated. Invest in failover automation that can be tested during disaster recovery drills under simulated stress situations.

5. Reveals Gap in Observability

During disaster recovery drills, it is often realized that metrics and logs from failover regions are incomplete and delayed. Not having good observability on the failover stack is dangerous and reduces visibility into the recovery process.

Key takeaway: Ensure primary and failover stack have full parity in terms of observability. Metrics, dashboard, and alert must be mirrored for both primary and failover stack.

6. Capacity Assumptions Are Wrong

Disaster recovery will not be successful just by having another region. It is also important to remember that a failover region can also handle the expected traffic. During a disaster recovery drill, teams discover issues with autoscaling configurations or quota capacity limits that are out of sync with the primary region.

Key takeaway: During disaster recovery drills, often conduct load-intensive tests that validate scaling policies and other limits that would not be exposed by performing only functional tests.

7. DNS and Routing Can Take Longer to Reflect

During failover operation traffic is rerouted to the failover region by updating DNS records. DNS value propagation relies on DNS TTLs and CDN cache invalidations, which introduce unpredictable latency.

Key takeaway: Keep the DNS TTL low to reduce DNS propagation time. Test DNS propagation speed in advance.

8. Build Redundancy Around People and Roles

Long disaster recovery drills that stretch over hours can cause fatigue in people involved. This can also lead to costly mistakes.

Key takeaway: Define secondary owners in advance for critical roles who can take over the drill and ensure redundancy. Fresh resources will prevent burnout and ensure timely and effective resolution.

9. Cost vs. Recovery Time Tradeoffs

Passive regions and over-provisioned capacity can be expensive. Many teams don’t realize the ongoing cost of maintaining hot-standby infrastructure until full failover is simulated. If infrastructure is under-provisioned, then it will involve more time to bring up infrastructure that will negatively impact recovery time.

Key takeaway: Use disaster recovery drills to evaluate cost-versus-recovery-time trade-offs. Teams can optimize by running a mix of active-active and active-passive topologies: critical workloads on active-active, and non-critical workloads on active-passive.

10. Disaster Recovery Drill Never Ends–Continuous Learning Is the Key

Every disaster recovery drill exposes a new issue. The organizations that fix the issue by closing the loop can truly improve. Keep track of learnings with clear ownership assigned for issues and track them until closed. These issues can reveal gaps in system architecture, or failover runbook and automations.

Key takeaway: Treat disaster recovery drills like mock incidents. Perform blameless post-mortems and root cause analysis to generate action items. Feed any new learnings into design and automation improvements.

Conclusion

Disaster recovery drills do more than validate systems — they reveal organizational weakness, improve coordination, and highlight areas of improvement. Organizations must treat disaster recovery drills as a learning exercise and not just another compliance checkbox. This mindset will enable organizations to build a more scalable and robust system that can withstand real incidents.

Remember: In disaster recovery, preparation is only as good as the practice. Disaster recovery drills are often learned continuously, and systems, processes, and teams will thank you when disaster strikes.