Disaster Recovery Concepts and Principles
What the exam tests
This domain checks whether you can distinguish DR from adjacent disciplines and use recovery objectives to drive decisions. Expect questions on RTO, RPO, MTPD, recovery tiers, and the principles that make a DR capability credible.
Core rules
- DR restores prioritized technology and data services after disruption; BCM coordinates the whole organization; incident management stabilizes the event.
- MTPD is the maximum tolerable period of disruption. RTO is the target time to resume; it must be shorter than MTPD, allowing time for damage assessment and declaration.
- RPO defines tolerable data loss measured in time. It constrains backup and replication design, not backup frequency alone.
- Recovery must be business-driven, risk-based, all-hazards, documented, exercised, and continually improved.
- Recovery tiers allocate investment: Tier 1 gets low RTO/RPO; lower tiers can tolerate manual workarounds.
Worked example
An order system has an MTPD of 8 hours, an RTO of 4 hours and an RPO of 15 minutes. A nightly backup gives a 24-hour RPO, so it fails the objective. The team proposes hourly log shipping plus warm standby. Reasoning: a 4-hour RTO leaves 4 hours for assessment and declaration before MTPD; a 15-minute RPO requires continuous or frequent replication. If replication cost is prohibitive, revisit the business-approved RPO - do not silently redefine it.
Traps
Confusing RTO with MTPD; treating RPO as “backup every 15 minutes” without testing restore; assuming DR is only IT; writing a plan before selecting a strategy; and claiming “zero downtime” without evidence.