6.1 The 7 Rs of Cloud Migration
Key Takeaways
- The 7 Rs are migration strategies: Retire, Retain, Relocate, Rehost (lift-and-shift), Replatform (lift-tinker-and-shift), Repurchase (drop-and-shop), and Refactor (re-architect).
- Rehost (lift-and-shift) is the fastest migration approach — move applications as-is to EC2 without code changes.
- Replatform makes minor optimizations during migration (e.g., moving from self-managed MySQL to RDS) without changing core architecture.
- Refactor/Re-architect offers the most long-term benefit by redesigning applications to be cloud-native (serverless, microservices) but takes the most time.
- AWS Application Migration Service (MGN) automates lift-and-shift migrations to AWS with minimal downtime.
Last updated: March 2026
The 7 Rs of Cloud Migration
Quick Answer: The 7 Rs are migration strategies ordered from simplest to most transformative: Retire (decommission), Retain (keep on-premises), Relocate (move to VMware Cloud on AWS), Rehost (lift-and-shift to EC2), Replatform (move with minor optimizations), Repurchase (switch to SaaS), Refactor (re-architect for cloud-native).
The 7 Migration Strategies
| Strategy | Description | Effort | Benefit | Example |
|---|---|---|---|---|
| Retire | Decommission applications no longer needed | Lowest | Cost reduction | Legacy app with no users |
| Retain | Keep on-premises (not ready to migrate) | Low | None (deferred) | App with complex dependencies |
| Relocate | Move to VMware Cloud on AWS | Low | Same VMware tools | VMware-based workloads |
| Rehost | Lift-and-shift to EC2 (no changes) | Low-Med | Quick migration | Web server → EC2 |
| Replatform | Lift-tinker-and-shift (minor optimizations) | Medium | Some cloud benefits | MySQL → RDS, Java app → Beanstalk |
| Repurchase | Replace with SaaS product | Medium | Reduced ops | On-prem CRM → Salesforce |
| Refactor | Re-architect for cloud-native | Highest | Maximum cloud benefit | Monolith → microservices + Lambda |
When to Use Each Strategy
| Scenario | Best Strategy |
|---|---|
| "Migrate 500 servers to AWS as fast as possible" | Rehost (lift-and-shift) |
| "Move our database to a managed service" | Replatform (to RDS/Aurora) |
| "We want to go serverless" | Refactor |
| "This app is no longer used" | Retire |
| "Too complex to migrate right now" | Retain |
| "Replace our email server" | Repurchase (to Amazon WorkMail or Office 365) |
AWS Migration Services
| Service | Purpose |
|---|---|
| AWS Migration Hub | Central tracking for all migration activities |
| AWS Application Migration Service (MGN) | Automated lift-and-shift for servers |
| AWS Database Migration Service (DMS) | Migrate databases with minimal downtime |
| AWS Schema Conversion Tool (SCT) | Convert database schemas between engines |
| AWS DataSync | Transfer data between on-premises and AWS storage |
| AWS Snow Family | Physical devices for large data transfers |
| AWS Transfer Family | SFTP/FTPS/FTP service backed by S3/EFS |
AWS Application Migration Service (MGN)
| Feature | Detail |
|---|---|
| Type | Automated lift-and-shift |
| How | Continuous block-level replication from source to AWS |
| Cutover | Non-disruptive cutover with minimal downtime |
| Supported | Physical, virtual, and cloud servers |
| Target | EC2 instances |
| Testing | Launch test instances without affecting source |
AWS Database Migration Service (DMS)
| Feature | Detail |
|---|---|
| Type | Database migration (homogeneous and heterogeneous) |
| Source | On-premises, EC2, RDS, Aurora, S3, and more |
| Target | RDS, Aurora, DynamoDB, S3, Redshift, and more |
| Replication | Continuous data replication (CDC) for minimal downtime |
| Homogeneous | Same engine (MySQL → MySQL) — no SCT needed |
| Heterogeneous | Different engine (Oracle → PostgreSQL) — use SCT first |
On the Exam: "Migrate an Oracle database to Aurora PostgreSQL" → SCT to convert the schema + DMS for data migration. "Migrate MySQL to RDS MySQL" → DMS only (homogeneous).
Test Your Knowledge
A company needs to migrate 200 servers to AWS as quickly as possible with minimal changes. Which migration strategy should they use?
A
B
C
D
Test Your Knowledge
A company wants to migrate an Oracle database to Amazon Aurora PostgreSQL. Which AWS services should they use?
A
B
C
D