How a Customer Upgraded over 2,000 Microsoft Windows Server 2016 to 2025 on Amazon EC2

This article details how a financial services customer upgraded over 2,000 Windows Server 2016 EC2 instances to Windows Server 2025 before January 2027 end-of-support deadline.

• Three upgrade options evaluated: fresh instance migration, clone-and-upgrade, in-place upgrade
• Customer chose in-place upgrade to preserve IP addresses, hostnames, and network configurations
• Critical prerequisites: convert licensing model to License Included, update EC2Launch v1 to v2
• AWS Systems Manager automation document automates validation, backup, upgrade, and post-upgrade tasks
• In-place upgrade requires 1-2 hour downtime window per instance
• EBS snapshots provide rollback capability if issues occur
• Best practices include testing in dev/test first and maintaining licensing compliance monitoring

The in-place upgrade approach with automation enabled the customer to efficiently upgrade their entire fleet while minimizing operational complexity and preserving existing network configurations.