Design Business Continuity Solutions – AZ-305 Study Guide
This domain accounts for 15–20% of the exam and covers designing backup, disaster recovery, and high availability to meet RTO/RPO objectives. The exam gives recovery requirements and asks for the right combination of Azure Backup, Azure Site Recovery, availability zones, region pairs, and database/storage replication. Master the RTO/RPO vocabulary and the availability-zone-vs-region-pair distinction and this domain is high-yield.
RTO and RPO — the Design Drivers
- RTO (Recovery Time Objective) — maximum acceptable downtime to restore service.
- RPO (Recovery Point Objective) — maximum acceptable data loss (how far back you may lose data).
Every business-continuity recommendation is judged against these two numbers. Tight RPO → synchronous replication; tight RTO → automated, orchestrated failover.
Backup vs Disaster Recovery
Two distinct services the exam loves to contrast:
| Service | Purpose | Recovers |
|---|---|---|
| Azure Backup (Recovery Services vault) | Scheduled, policy-driven, application-consistent backups with retention | Data (point-in-time) |
| Azure Site Recovery (ASR) | Continuous replication + orchestrated failover to a secondary region | Running workloads (DR) |
- Azure Backup protects Azure VMs, on-premises servers, databases, and Azure Files with backup policies (schedule + retention, including long-term multi-year retention).
- Azure Site Recovery replicates VMs to a secondary region for regional DR, supports test failover (validate DR in an isolated network without disrupting production), and meets tighter RTO/RPO than periodic backups.
"Weekly backup" can't meet a 15-minute RPO — that requires replication (ASR or synchronous DB replication).
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