SQL Server to Azure SQL Migration
I executed a zero-downtime migration of a 2TB SQL Server database from on-premises to Azure SQL Database, with complete application compatibility.
At a glance
- •Cutover downtime: 4 minutes (read-only)
- •Monthly infra costs: -35%
- •RTO: 4 hours → 15 minutes
Problem Statement
A manufacturing company needed to migrate their mission-critical ERP database from an aging on-premises SQL Server 2012 to Azure SQL Database. The system runs 24/7 with no maintenance windows. They needed continuous operation during migration and the ability to roll back if things went wrong.
Architecture & Design
I designed a phased migration using Azure Data Migration Service for minimal downtime. The strategy included initial full database migration, continuous data sync during prep, and planned application endpoint switch. Set up Azure SQL Database with proper service tier sizing and geo-replication for disaster recovery.
Implementation Details
I ran compatibility assessment using Data Migration Assistant to find and fix compatibility issues. Set up Azure Data Migration Service to continuously replicate changes during migration. Did multiple rehearsal migrations to refine the process and timing. Coordinated with app teams for connection string updates and DNS changes. Implemented monitoring to track replication lag.
Results & Outcome
Migration completed with only 4 minutes of read-only downtime and zero data loss. Monthly infrastructure costs dropped 35% through Azure's managed services. Disaster recovery improved from 4-hour RTO to 15-minute RTO using geo-replication. Database performance got better through Azure's automatic tuning. Client achieved SOC 2 compliance faster with Azure's built-in security.