LEARN. PRACTICE. GROW.Concept and mechanism
Zone redundancy protects against zonal failures within a region; continuity through regional loss requires a different protection scope. Failover groups use geographic replication and listeners that follow roles. Planned and forced failover have different conditions and risks. If primary is unreachable, transactions not yet replicated may be lost when secondary is promoted. Online does not mean fully synchronized. Use the read-write listener for writes and validate DNS, reconnection, and safe retries. Existing sessions do not magically become completed transactions at the new destination. Customer-managed and Microsoft-managed policies also have distinct expectations; do not promise identical RTO for every configuration. Record the decision owner and acceptable loss before an incident.
Guided application
In a fictional VM design, distinguish FCI, which protects an instance using shared storage, from availability groups using database replicas with separate copies. Log shipping sends and restores log backups for recovery with its own operational workflow. None of these labels replaces assessment of regions, networking, quorum, identity, and jobs. During DR rehearsal, time application return rather than database opening alone. If DNS or keys add an hour, that time forms part of the business outcome. APS handover needs a runbook, alerts, escalation criteria, rehearsal evidence, owners, and reconciliation after possible loss. Record risks that still prevent RUN autonomy and assign concrete corrective actions.
Database open after 15 minutes + application operational 60 minutes later = 75 minutes to useful service in this fictional case.
Common pitfalls
Zone as region; Online as synchronized; listener as failure-free transaction; database-only RTO.
Related topics: Platform, capacity, and migration · Identity, networking, and encryption · Sensitive data and evidence
Recovery ends when service meets agreed criteria.
Reference: Failover groups and listener endpoints · DP-300 English objectives effective 2026-04-24