Testing Your DR Plan: How Often, What to Test, and What Breaks

A DR plan you haven't tested is a document, not a plan. This piece covers the four types of DR tests, how often to run each one, what to validate during each test, and specific things that have broken during tests I've either run or observed. The testing frequency matrix below is a starting point — adjust it based on your environment and risk tolerance.

The Four Types of DR Tests

Each serves a different purpose. You need all four.

1. Tabletop exercise. A conference room walkthrough. No systems are touched. The team reads through the recovery procedures step by step and identifies gaps: missing steps, outdated references, unclear ownership. Time required: 2–4 hours. Disruption: zero.

2. Component test. Pick one system. Restore it from backup. Verify the application starts and the data is intact. This validates that your backups are actually usable — not just that the backup job completed. Time required: 2–8 hours depending on system size. Disruption: minimal if you restore to an isolated environment.

3. Parallel test. Bring up the full recovery environment alongside production. Run traffic through it. Confirm that the recovered stack performs as expected without cutting over production. Time required: 1–2 days. Disruption: moderate (requires coordination and dedicated resources).

4. Full failover test. Switch production to the DR environment. This is the real thing. Users are on the DR stack. Time required: 4–12 hours of cutover plus a maintenance window. Disruption: high. Necessary: yes, at least annually for Tier 1 systems.

Testing Frequency Matrix

This matrix shows minimum recommended frequencies by system tier. Tier 1 systems are revenue-generating or customer-facing. Tier 2 are important internal systems. Tier 3 are everything else.

Tier 3 systems: component test annually. Tabletop only otherwise. Don't waste testing cycles on systems that can tolerate multi-day outages.

What to Validate During Each Test

Running the test isn't enough. You need to validate specific things. Here's the checklist:

• Backup data restores without corruption errors
• Application starts and serves requests after restore
• Database integrity checks pass (row counts, checksums)
• Dependent services can reach the recovered system
• DNS and network routing function correctly in the DR environment
• Authentication works — user accounts, service accounts, API keys
• SSL certificates are valid in the DR environment
• Monitoring and alerting is active in the DR environment
• Actual recovery time is measured and compared against the RTO target
• Runbook steps match reality — no references to decommissioned resources
• Communication chain works — the right people were reached in the right order

Document every validation result. Pass or fail. If something fails, that's not a bad test — that's a successful test that found a gap. You want to find gaps in testing, not during a real incident.

Field Notes: What Actually Breaks

I've been involved in DR testing at eight organizations over the past four years. Here's what breaks most often.

DNS. Every time. The recovered environment comes up, but DNS still points to the production IP addresses. Or the TTL is set to 24 hours and propagation takes longer than the RTO. Lesson: include DNS cutover in the runbook and verify the TTL before the test.

Service accounts and credentials. The application starts, but it can't authenticate to the database because the service account password was rotated three months ago and the DR configuration still has the old one. This is especially common when secrets are managed outside the backup scope.

Capacity mismatches. The DR environment was spec'd two years ago for the data volume at that time. Production has grown 40% since then. The restore completes but the DR disks are at 94% capacity, performance degrades, and the team spends two hours troubleshooting before realizing it's just disk I/O saturation.

Restore time surprises. The plan says "4-hour RTO." The actual restore takes 7.5 hours because nobody tested at current data volumes. The estimates were based on a test from 18 months ago with 30% less data. Always re-benchmark restore times when data volumes change significantly.

Sequence errors. System A depends on System B, but the runbook restores them in parallel. System A comes up, can't find System B, throws errors, auto-retries hit their limit, and the application enters a bad state that requires a manual restart. Map and document recovery sequence. Test the sequence, not just the individual systems.

When Testing Isn't Worth the Effort

There are diminishing returns. Testing your email system's DR monthly is probably overkill if your RTO for email is 48 hours. Testing Tier 3 systems that can be rebuilt from scratch in a few hours doesn't warrant full parallel tests. Be honest about where your risk actually lies and focus testing cycles on the systems where a failure would cause real damage.

Also: if you're a small team — fewer than five people in IT — full failover tests are likely impractical. Focus on component tests and tabletops. A monthly "pick one system, restore it, verify it works" cycle will catch most problems. The common mistakes piece covers the specific failure patterns this prevents.