Cloud Concepts · Topic 3 of 4
Migration Strategies and the CAF
Learn why companies migrate to AWS, the migration strategies called the Rs, the Cloud Adoption Framework perspectives and the main AWS migration tools.
- 4 min
- The CAF perspectives are business, people, governance, platform, security and operations.
- Rehost is lift and shift. Replatform is a small tweak. Refactor is a redesign.
- Repurchase usually means moving to a SaaS product.
What it is
Migration means moving applications, data and workloads from an existing environment, usually an on premises data center, to AWS.
Companies migrate to save cost, gain agility, improve resilience or retire old hardware. The exam asks which strategy suits a situation, which framework guides planning, and which tool does a given job.
AWS offers the AWS Cloud Adoption Framework (CAF) as planning advice, a set of migration strategies, and several services that move servers, databases and data.
How it works
Cloud Adoption Framework perspectives
The CAF groups its advice into perspectives, which are areas of responsibility inside an organisation.
| Perspective | Concerned with |
|---|---|
| Business | Strategy, value and how the cloud supports business goals |
| People | Skills, training and organisational change |
| Governance | Managing risk, cost and portfolio priorities |
| Platform | Building and operating the technical environment |
| Security | Protecting data and meeting security goals |
| Operations | Running, monitoring and supporting workloads day to day |
A simple way to place them is that business, people and governance are business side perspectives, while platform, security and operations are technical side perspectives.
Migration strategies (the Rs)
| Strategy | Meaning | Typical use |
|---|---|---|
| Rehost | Move as is, often called lift and shift | Fast move with little change |
| Replatform | Make small changes to gain a benefit | Move a self-managed database to a managed one |
| Repurchase | Replace with a different product, often software as a service (SaaS) | Swap an old customer relationship management (CRM) system for a SaaS product |
| Refactor | Redesign the application to use cloud native features | Gain scale and agility, but it takes the most effort |
| Retire | Switch off what is no longer needed | Remove unused applications |
| Retain | Leave it where it is for now | Not ready or not worth moving |
| Relocate | Move a whole platform to its cloud version without rewriting | Move VMware based servers in bulk |
Older material lists six Rs and leaves out Relocate, so you may see either list.
Rehost is fastest. Refactor delivers the most cloud benefit but costs the most time and skill.
Migration tools
| Tool | Purpose |
|---|---|
| AWS Migration Hub | One place to track migrations across tools |
| AWS Application Discovery Service | Collects information about on premises servers and dependencies |
| AWS Application Migration Service | Rehosts servers onto AWS |
| AWS Database Migration Service (DMS) | Moves databases, including between different engines |
| AWS Schema Conversion Tool | Converts a database schema when the engine changes |
| AWS DataSync | Transfers large amounts of file data over the network |
| AWS Snow Family | Physical devices to move data when the network is too slow |
| AWS Transfer Family | Moves files using standard transfer protocols such as the Secure File Transfer Protocol (SFTP) |
| AWS Migration Evaluator | Builds a business case from current usage |
Moving large amounts of data
When data is huge or bandwidth is small, shipping physical Snow Family devices can be faster than sending it over the network. For ongoing transfers, a network service such as DataSync or a dedicated line suits better.
Benefits of migration
- Lower cost and less spending on hardware refreshes.
- Faster delivery of new features.
- Better resilience with multiple data centers.
- A path to modern services such as managed databases and machine learning.
What to remember for the exam
- The CAF perspectives are business, people, governance, platform, security and operations.
- Rehost is lift and shift. Replatform is a small tweak. Refactor is a redesign.
- Repurchase usually means moving to a SaaS product.
- Retire removes applications. Retain keeps them where they are.
- Application Discovery Service finds servers and dependencies, and Migration Hub tracks progress.
- Application Migration Service rehosts servers. Database Migration Service moves databases.
- The Snow Family moves data physically when the network is not practical.
- Migration Evaluator helps create a business case before moving.
A question that says "with the least effort and no code changes" points to rehost. One that says "take advantage of cloud native features" points to refactor.
Common mistakes
Choosing refactor for speed. Refactor is the slowest strategy, so it rarely fits a tight deadline.
Mixing up the CAF and the Well-Architected Framework. The CAF guides an organisation through adoption. The Well-Architected Framework reviews how a specific workload is built.
Confusing DMS with DataSync. DMS moves databases. DataSync moves file and object data.
Forgetting retire and retain. A good migration plan also decides which systems to switch off or leave alone.
Shipping data on a Snow Family device is not the same as using AWS Direct Connect. Snow devices are one time physical transfers, while Direct Connect is a dedicated network link.
Check yourself
Which migration strategy moves an application as is with little change?
Rehost, also called lift and shift.
Which CAF perspective covers skills and training?
The People perspective.
Which service helps move a database to AWS, even between engines?
AWS Database Migration Service, with the Schema Conversion Tool when the schema must change.
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