Practical Lift-and-Shift Migration with AWS Application Migration Service (MGN)
A practical guide to lift-and-shift migration from agent installation to cutover, covering design considerations and network configuration.
How MGN Works and Its Benefits
AWS Application Migration Service (MGN) is a service for lift-and-shift migration of on-premises or other-cloud servers to AWS. After installing a lightweight replication agent on the source server, it continuously replicates disk contents to AWS at the block level in real time. The source server continues to operate normally during replication, so downtime is limited to just a few minutes during cutover. Unlike the legacy Server Migration Service (SMS), which used periodic snapshot-based synchronization, MGN uses continuous replication to bring the RPO close to zero.
Migration Steps - From Agent Installation to Cutover
Migration proceeds in four phases. Phase 1 is agent installation. Installing the AWS Replication Agent on the source server registers it in the MGN console and starts the initial sync. Phase 2 is launch settings configuration. You define the instance type, VPC, subnet, security group, IAM role, and other settings in a launch template. Phase 3 is test launch. You launch a test EC2 instance to verify application behavior, network connectivity, and performance. If issues arise, you can modify the launch settings and retest. Phase 4 is cutover. A final data sync is performed, and the production EC2 instance is launched. Traffic is redirected to the new environment by updating DNS records or load balancer configurations.
Design Considerations
Replication requires a stable network connection from the source server to AWS. As a bandwidth guideline, replicating 100 GB of disk within 24 hours requires approximately 10 Mbps. Connecting via Direct Connect or VPN is recommended. The replication staging area automatically creates lightweight EC2 instances (around t3.small) and EBS volumes. This cost is roughly a few dollars per month per source server. For large-scale migrations, it is important to use Migration Hub to centrally track progress, group servers by application, and cut over interdependent servers simultaneously. For more detailed coverage of server migration, related books on Amazon are a helpful resource.
MGN Pricing
MGN itself is free, with no additional charges for agent installation or continuous replication. Costs come from the replication staging area (lightweight EC2 instances and EBS volumes). Test instance launches incur EC2 charges at the target spec, so terminate them promptly after testing. After cutover, stop replication and delete staging area resources to eliminate unnecessary costs.
Summary
MGN is the standard tool for lift-and-shift migration, delivering minimal-downtime migration through agent-based continuous replication. Simply installing an agent on the source server starts block-level replication, and test instance launches allow pre-migration validation. Cutover downtime is typically just a few minutes, and the service scales to support large migration projects.