Author and execute a single DR drill for one service: author the runbook (per-tier RTO + RPO), pre-drill checklist (data sync state, alert silencing, customer comms), drill workflow (announce, fail-over, verify, fail-back) with timestamps, standby verification, failback, and an auditor-ready post-drill report. Per Google Cloud DR planning guide; covers cold / warm / hot standby tier-specific patterns. For coordinating drills across multiple services or teams, use a multi-service drill orchestrator. Use when a scheduled or post-incident failover drill for one service is being planned, executed, or written up, or when a new tier-1 service ships without a drill defined.