Inventory all systems and dependencies. Migrate in waves: non-critical first, then DB and app. Use replication or sync to minimize cutover time. Document and test rollback for each wave.
Inventory and planning
- List everything: Servers, roles (app, DB, cache), DNS, firewall rules, backups, and dependencies (which app talks to which DB).
- Prioritize: Non-critical (staging, tools) first; then app tier; then DB and core services. Reduces risk and lets you refine the process.
- Dependencies: Migrate in order so that when app servers move, they can still reach DB and other services (or move DB first and point apps to the new location).
Waves and cutover
- Wave 1: Low-risk systems. Validate process, DNS cutover, and monitoring. Document issues and fix the playbook.
- Wave 2+: App servers; use replication or rsync to pre-copy data, then short cutover window. DB: use replication if possible so primary can fail over to new host with minimal downtime.
- Cutover: Final sync, switch DNS or load balancer, verify, then decommission old after a soak period.
Rollback and testing
- Rollback plan: For each wave, document how to revert (e.g. point DNS back, fail DB back to old primary). Test rollback once if possible.
- Validation: Smoke tests, health checks, and user acceptance after each wave. Keep old systems running until the wave is stable.
Summary
Inventory and plan waves (non-critical first, then app, then DB). Use replication/sync to minimize cutover; document and test rollback per wave. Validate each wave before moving on.
