Introduction
Cloud migration often looks simple on paper, “lift and shift the servers and run them on AWS.”
But architects know the reality is dramatically different.
Enterprise migrations involve multi-tier apps, interdependent services, legacy systems, compliance requirements, weekend cutovers, and the never-ending question “Will the application work exactly the same after cutover?”
AWS Application Migration Service (MGN) significantly simplifies rehosting, yet the architecture behind a scalable migration is where most projects struggle.
In this blog, I will walk through how to architect large migrations using AWS MGN, combined with Cloud Studio 2.0, an accelerator that helps automate discovery, dependency mapping, and migration wave planning (Cloud Studio is a Wipro’s proprietary tool/ Platform, Instead of Cloud Studio tool you can use other third-party tools as well based on your requirement and use case, example Matilda etc.). These approaches come from real-world programs supporting enterprise customers transitioning hundreds of servers to AWS.
Rehosting Strategy: Why It Still Matters
While modernization themes like containers, serverless platforms, or AI driven refactoring attract attention, the majority of enterprises still adopt rehosting as their first step toward cloud transformation. Rehost offers the fastest and least disruptive path to AWS because it minimizes code changes, reduces migration risk, and makes rollback straightforward. AWS MGN further strengthens this approach by enabling continuous block level replication, near zero downtime cutovers, and automated testing sequences. These capabilities make MGN the operational backbone for large migration programs with legacy workloads and strict performance requirements.
Understanding the AWS MGN Architecture
An effective migration architecture with AWS MGN brings together several coordinated components. Source servers running on VMware, Hyper V, physical hardware, or other environments install the MGN replication agent, which transfers data continuously to AWS. A lightweight staging area consisting of EC2 instances and Amazon EBS volumes receives and synchronizes this data, while a replication server manages ongoing transfers. When testing or cutover is initiated, MGN automatically provisions new instances according to predefined launch templates. This architecture enables real time replication that remains synchronized throughout the migration, supports repeated functional and performance validation, and allows teams to roll back without data loss. Architectural considerations typically involve choosing appropriate subnets for staging, determining instance types for testing and cutover, enforcing IAM boundaries for teams, and supporting cross account replication for regulated workloads. Together, these elements create a reliable and secure migration pipeline.
Discovery and Planning with Cloud Studio 2.0
When migrating large environments - often 100 servers or more, planning becomes as important as execution. Enterprises must understand system relationships, communication pathways, upstream and downstream dependencies, application grouping, and downtime constraints. Cloud Studio 2.0 addresses these gaps by discovering application topologies, identifying interdependencies, and automatically grouping systems into migration waves based on their connectivity and operational behavior. It provides effort and timeline estimations, generates standardized runbooks, and creates visibility into the sequencing required for each application. When combined with AWS MGN’s automated replication and cutover workflows, this planning foundation significantly reduces migration effort and improves predictability.
Reference Migration Architecture
Reference – https://aws.amazon.com/blogs/architecture/multi-region-migration-using-aws-application-migration-service/
Above blog illustrates a reference architecture for MGN that integrates discovery, replication, testing, and cutover processes into a cohesive design. The architecture ensures that data is continuously synchronized, test instances can be launched repeatedly, and production cutover occurs only after the application has been validated. This foundation allows enterprises to maintain confidence throughout migration waves, even when dealing with complex multi tier workloads.
Best Practices for Large Scale Migrations
Enterprise programs benefit from beginning replication well in advance of scheduled cutover windows. Early warm up enables synchronization to stabilize, surfaces potential bandwidth limitations or I/O constraints, and reduces the final cutover delta. Many organizations create dedicated accounts for staging, testing, and production to improve governance and isolation. Standardizing launch templates helps remove configuration drift across teams and workloads, ensuring test and cutover environments remain consistent. Multiple rounds of functional and performance testing improve reliability and reduce surprises during actual migration. After workloads land on AWS, MGN’s post cutover automation can remove migration agents, perform initial cleanup operations, join systems to domains, and establish security baselines, making Day 1 operations more efficient.
Real World Implementation Example
A global retailer migrating 115 servers across 23 interconnected applications faced several challenges including undocumented dependencies, restricted weekend downtime windows, and significant ongoing data transfer requirements. By using Cloud Studio 2.0 for automated discovery and migration wave planning, AWS MGN for continuous replication and cutover, and AWS Systems Manager for post migration activities, the retailer completed the migration with no rollback events. Planning effort reduced by more than half, and cutover completed smoothly within the approved downtime window. This outcome demonstrates the importance of strong pre migration discovery combined with automation throughout the migration cycle.
Conclusion
Large scale enterprise migrations require architectural clarity, structured planning, and automation at every stage. AWS Application Migration Service (MGN), when combined with Cloud Studio 2.0 or equivalent planning tools, provides a scalable blueprint for rehosting workloads efficiently and predictably. Whether migrating ten servers or one thousand, the principles outlined in this blog help organizations build a repeatable, low risk framework for transitioning applications to AWS and unlocking future modernization opportunities.
Please refer the blog to follow the MGN service Migration steps - https://aws.amazon.com/blogs/architecture/multi-region-migration-using-aws-application-migration-service/
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