Migrating VMs to AWS
Migrating VMs to AWS means lifting existing workloads—hypervisors, operating systems, and applications—and running them on AWS infrastructure with minimal redesign. Success depends on understanding the source environment, choosing the right migration path, and validating behavior after cutover. The process is repeatable, but each workload has its own constraints around licensing, dependencies, and downtime tolerance.
More from this site
Keep reading the latest coverage
Assess and Inventory
Start with a discovery pass that maps every VM to its business owner, resource profile, and interdependencies. Capture CPU, memory, storage, I/O patterns, network topology, and licensing terms. Tools like AWS Application Discovery Service and Azure Migrate can collect this data passively, reducing manual effort. Classify workloads into tiers—rehost, replatform, refactor—so each gets the appropriate AWS strategy.
Key questions to answer
- Which VMs must move first due to business priority?
- What are the peak and steady-state resource needs?
- Are there hardware dongles, MAC-based licenses, or host-bound software?
- What is the acceptable downtime window per workload?
Choose a Migration Path
AWS offers several paths. AWS Server Migration Service (SMS) replicates on-prem VMs into AMIs for straightforward rehosting. AWS VM Import/Export supports larger, more complex images and lets you bring custom AMIs into EC2. For workloads that can tolerate some modernization, AWS Application Migration Service (formerly CloudEndure Migration) provides application-consistent replication and automated conversion. The choice depends on image size, network bandwidth, licensing, and whether you want a near-identical copy or a lightly optimized AWS-native image.
| Path | Best For | Trade-off |
|---|---|---|
| AWS SMS | Simple, frequent VM replication | Limited to supported guest OS and instance types |
| VM Import/Export | Large or custom images | Manual image preparation and validation |
| AWS Application Migration Service | Near-zero-downtime, automated conversion | Requires agent installation and connectivity |
Networking and Connectivity
Before migration, design the target VPC so AWS resources can reach each other and any on-prem systems that remain. Plan subnets, security groups, NACLs, and routing so IP-dependent applications do not break. AWS Direct Connect or Site-to-Site VPN can keep hybrid connectivity during a phased cutover. DNS and time synchronization settings should be reviewed early; assumptions about local NTP or internal DNS can cause subtle post-migration failures.
Execute and Validate
Run a pilot migration with a low-risk VM to test tooling, bandwidth, and cutover procedures. After replication, boot the instance in AWS, run application tests, and compare performance against baseline metrics. Use AWS Systems Manager and CloudWatch to collect post-migration telemetry. Document deviations—such as changed MAC addresses or disk identifiers—and update configurations before scaling to the remaining fleet.
Optimize After Migration
Once workloads are stable, right-size instances based on actual utilization. Replace general-purpose instances with compute or memory-optimized types where appropriate. Consider EC2 Image Builder to harden and patch AMIs consistently, and evaluate AWS Backup or Amazon Data Lifecycle Manager for long-term protection. Migration is not a one-time event; continuous review keeps costs and performance aligned with demand.