AWS Application Migration Service (MGN)

1. Migration Strategies (The 7 Rs)

AWS defines 7 migration strategies, commonly called the "7 Rs." Choosing the right strategy depends on your application’s complexity, business requirements, and desired outcome.

Exam Focus on 7 Rs

The exam tests your ability to pick the right strategy for a scenario. "Fastest migration with no code changes" = Rehost. "Small optimizations, use managed services" = Replatform. "Redesign for cloud-native" = Refactor. "Replace with SaaS" = Repurchase. "Shut down unused apps" = Retire.

2. AWS Application Migration Service (MGN)

AWS MGN is the recommended service for lift-and-shift (rehost) migrations. It automates the process of migrating physical, virtual, or cloud servers to AWS.

Core Concept

MGN continuously replicates your source servers to AWS in the background. When you’re ready to cut over, MGN launches the replicated servers as EC2 instances in your VPC. Minimal downtime (typically minutes). No agents on the server OS — block-level replication at the storage layer.

How MGN Works

MGN Migration Flow:

1. INSTALL: Install AWS Replication Agent on source server
2. REPLICATE: Agent replicates data to AWS continuously (block-level)
   - Initial sync: full copy of all disks
   - Ongoing: continuous replication of changes (near real-time)
3. TEST: Launch test instances in AWS to validate
   - Non-disruptive (source server keeps running)
4. CUTOVER: Final replication + launch production instances
   - Brief cutover window (minutes)
   - Point DNS/Load Balancer to new AWS instances
5. FINALIZE: Decommission source servers

Key Features

1. Continuous block-level replication (not snapshot-based)
2. Supports: physical servers, VMware, Hyper-V, Azure VMs, other cloud VMs
3. Supported OS: Windows Server, Amazon Linux, Ubuntu, RHEL, CentOS, SUSE, Debian, etc.
4. Automated conversion: server → EC2 instance (correct drivers, boot config)
5. Non-disruptive testing: test in AWS while the source keeps running
6. Minimal cutover downtime (typically minutes)
7. Post-launch actions: run scripts automatically after instance launches (install agents, configure)
8. Free: no charge for MGN service (you pay for replication EC2 instances + EBS)

MGN Architecture

MGN Architecture:

Source Environment              AWS

  Source Server          Staging Area (auto-created)
  [OS + App + Data]      [Replication Server]
       |                      |
  Replication Agent ─────→ Lightweight EC2
  (block-level)          + EBS volumes (replica)
       |                      |
  Continuous sync         On cutover:
  (encrypted TLS)         Launch Target EC2
                          in your VPC
                          (production-ready)

3. MGN vs Other Migration Tools

Exam Tip MGN: "Lift & shift migration" = MGN. "Rehost servers to EC2" = MGN. "Continuous replication" = MGN. "Minimal downtime cutover" = MGN. "Migrate databases" = DMS (not MGN). "Large offline data transfer" = Snow Family. "File storage sync" = DataSync. MGN replaces CloudEndure. MGN is free (pay for EC2/EBS only).