No business is immune to disruption. Hardware failures, ransomware attacks, natural disasters, and human error can all bring operations to a halt. A well-tested Disaster Recovery (DR) plan is the difference between a minor incident and a business-threatening crisis. This guide walks you through building one from scratch.
Understanding Disaster Recovery Fundamentals
Key Metrics: RTO and RPO
Before designing any DR solution, you must define two critical targets:
- Recovery Time Objective (RTO): The maximum acceptable time your systems can be offline after a disaster. If your RTO is 4 hours, you must be able to restore operations within 4 hours.
- Recovery Point Objective (RPO): The maximum acceptable amount of data loss measured in time. An RPO of 1 hour means you can afford to lose at most 1 hour of data.
These two figures drive every technology and process decision in your DR plan. A business requiring RTO of 15 minutes and RPO of zero will spend far more than one accepting RTO of 24 hours and RPO of 4 hours.
DR vs Business Continuity
Disaster Recovery focuses on restoring IT systems and data. Business Continuity Planning (BCP) is broader—it covers how the entire organisation continues to function during and after a disruption, including people, premises, and processes. Your DR plan should sit within a wider BCP framework.
Step 1: Business Impact Analysis (BIA)
A BIA identifies which systems and processes are critical to your business and quantifies the impact of their failure.
What to Document
- All IT systems and the business processes they support
- Revenue impact per hour of downtime for each system
- Regulatory or contractual obligations requiring specific recovery times
- Dependencies between systems (e.g., CRM depends on database server)
Output
A priority-ranked list of systems with RTO and RPO targets for each. Typically:
| Priority | System Type | RTO | RPO |
|---|---|---|---|
| Tier 1 (Critical) | Core business apps, financial systems | < 1 hour | Near-zero |
| Tier 2 (Important) | Email, collaboration, secondary databases | 4–8 hours | 1–4 hours |
| Tier 3 (Standard) | Development, test, analytics systems | 24–72 hours | 24 hours |
Step 2: Identify Threats and Risks
Document the specific threats your organisation faces:
- Technical failures: Hardware failure, software corruption, network outages
- Cyber incidents: Ransomware, data breach, DDoS attack
- Human error: Accidental deletion, misconfiguration
- Natural disasters: Flooding, fire, power outage
- Third-party failures: ISP outage, cloud provider incident, key vendor failure
For each threat, assess the likelihood and potential impact using a simple risk matrix.
Step 3: Choose Your DR Strategy
Backup and Restore
The simplest and cheapest strategy. Data is backed up and restored when needed. Suitable for Tier 3 systems only—RTOs are measured in hours to days.
Best practice: Follow the 3-2-1-1-0 rule:
- 3 copies of data
- 2 different storage media
- 1 offsite copy
- 1 offline/air-gapped copy
- 0 backup errors (verify regularly)
Pilot Light
A minimal version of your environment is always running in the cloud. In a disaster, you scale it up quickly. Suitable for Tier 2 systems with RTOs of 1–4 hours.
Warm Standby
A scaled-down but fully functional version of your environment runs continuously. Failover is fast (minutes to 1 hour). More expensive than pilot light but significantly faster recovery.
Hot Standby / Active-Active
Full duplicate environment running simultaneously with real-time data replication. Near-zero RTO and RPO. Reserved for Tier 1 mission-critical systems due to cost.
Step 4: Select DR Technologies
Cloud-Based DR
Cloud platforms have democratised enterprise-grade DR:
- Azure Site Recovery: Replicates VMs to Azure with orchestrated failover
- AWS Elastic Disaster Recovery: Continuous replication with point-in-time recovery
- Veeam: Backup and replication for hybrid environments
- Zerto: Continuous data protection with journal-based recovery
Backup Solutions
- Cloud backup: Azure Backup, AWS Backup, Backblaze B2
- On-premises: Veeam, Commvault, Acronis
- SaaS backup: Spanning (Microsoft 365), Backupify (Google Workspace)
Step 5: Write the DR Runbook
A runbook is a step-by-step, role-specific guide for executing recovery procedures. A good runbook:
- Is written so that someone unfamiliar with the system can execute it
- Includes exact commands, URLs, credentials locations (not the credentials themselves)
- Specifies who is responsible for each step
- Includes estimated time for each step
- Has a communications template for notifying stakeholders
Runbook Structure
- Incident declaration criteria
- Immediate containment steps
- Assessment and decision tree
- Recovery procedure (step-by-step)
- Verification checklist
- Stakeholder communication template
- Post-incident review process
Step 6: Test Your DR Plan
An untested DR plan is not a DR plan—it is a document. Testing must be scheduled, documented, and acted upon.
Types of DR Tests
| Test Type | Description | Disruption |
|---|---|---|
| Tabletop exercise | Walk through the plan verbally | None |
| Walkthrough test | Review procedures with team | None |
| Simulation test | Simulate a specific failure scenario | None |
| Parallel test | Activate DR systems alongside production | Low |
| Full failover test | Cut over to DR environment completely | High |
Recommended cadence: Tabletop quarterly; full failover test annually for critical systems.
Step 7: Maintain and Improve
Your DR plan becomes outdated the moment your infrastructure changes. Establish a maintenance programme:
- Review and update after every significant infrastructure change
- Update contact lists and escalation procedures quarterly
- Run a lessons-learned review after every real incident or test
- Track and remediate all gaps identified in testing
A disaster recovery plan is only as good as your last successful test. Invest the time to test thoroughly, and you will have genuine confidence when you need it most.