What are Cloud Migration Strategies (6 R's of Cloud)?

When an organization decides to move its applications and data from traditional on-premises environments to the AWS Cloud, it typically chooses from a set of common migration strategies.

These strategies, often referred to as the "6 Rs," help categorize and plan the approach for each application, balancing speed, effort, and the degree of cloud optimization.

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Definition:

• Migration strategies are the different approaches an organization can take to move existing applications, workloads, and data from their current on-premises or traditional hosting environments to a cloud platform like AWS.
• The "6 Rs" (Rehosting, Replatforming, Refactoring, Repurchasing, Retaining, Retiring) provide a framework for classifying these approaches.

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How It Works & Core Attributes (The 6 Rs):

Each "R" represents a distinct strategy with varying levels of effort, cost, and cloud-native optimization:

1. Rehosting (Lift and Shift):

• Focus: Moving applications as-is from on-premises to the AWS Cloud, typically to Amazon EC2 instances. This involves minimal changes to the application's architecture or code.
• Characteristics: It's often the fastest and least complex migration strategy. It allows organizations to quickly exit their data centers and realize initial cloud benefits.
• Trade-off: While fast, it may not fully leverage cloud-native features immediately, potentially limiting optimization.
• Think: Move quickly without changing anything.

2. Replatforming (Lift and Tinker):

• Focus: Moving applications to AWS, but making some cloud-native optimizations to achieve tangible benefits without fundamentally changing the core architecture.
• Characteristics: This could involve updating an operating system, moving from a self-managed database to a fully managed AWS database service (like Amazon RDS), or using AWS Elastic Load Balancing instead of a traditional load balancer.
• Benefit: Provides more cloud benefits than rehosting with relatively low effort compared to re-architecting.
• Think: Move, but make some small, beneficial upgrades.

3. Refactoring/Re-architecting:

• Focus: Rearchitecting the application to fully leverage cloud-native features and optimize for scalability, performance, and cost. This involves significant changes to the application's code and design.
• Characteristics: Often involves breaking down monolithic applications into smaller, independent microservices, or adopting serverless functions (like AWS Lambda). This strategy is driven by a strong business need to add features, scale, or improve agility that is not possible in the existing environment.
• Benefit: Maximizes the long-term benefits of cloud computing.
• Think: Completely rebuild for the cloud to gain maximum advantage.

4. Repurchasing:

• Focus: Moving from an existing application or license model to a new, cloud-native Software as a Service (SaaS) product.
• Characteristics: This means replacing an application with a managed third-party service (e.g., moving from an on-premises CRM to Salesforce, or an on-premises email server to Microsoft 365).
• Benefit: Eliminates the need to operate any infrastructure, greatly reducing operational overhead.
• Think: Replace your old solution with a ready-to-use cloud service.

5. Retaining (Revisiting):

• Focus: Deciding not to migrate certain applications to the cloud and keeping them on-premises.
• Characteristics: This might be due to specific compliance requirements, significant refactoring costs that outweigh the cloud benefits, a pending application replacement, or a specific dependency that cannot move.
• Implication: Acknowledge that not everything will (or should) move to the cloud immediately.
• Think: Keep some things exactly where they are.

6. Retiring:

• Focus: Decommissioning applications that are no longer needed or no longer provide business value.
• Characteristics: This is a crucial step that often occurs during the discovery phase of a migration. Identifying and retiring unused resources avoids migrating unnecessary workloads and incurring redundant costs in the cloud.
• Benefit: Reduces the overall migration effort and saves costs by eliminating unnecessary infrastructure.
• Think: Get rid of what you no longer need.

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Analogy: Moving Your Entire Business to a New Digital City (Focus on Moving Options)

Imagine your business operations are currently housed in a traditional office building in an old city.

You've decided to move to a new, modern, digital city (the AWS Cloud). The "6 Rs" are your various moving options:

• Rehosting: You hire movers to literally pick up all your existing office furniture and files and place them into a new digital building, exactly as they were. Quickest, least hassle for your stuff.
• Replatforming: You move your furniture, but also take the opportunity to replace some old, clunky desks with modern standing desks or upgrade your old filing cabinets to smart digital ones, just a few improvements as you move.
• Refactoring: You decide the old furniture and office layout won't work in the new digital building. So, you sell everything, completely redesign your workflow, and buy brand-new, purpose-built furniture that perfectly fits the modern digital workspace. Most transformative, but highest initial effort.
• Repurchasing: Instead of moving your old office's accounting software, you cancel that service and subscribe to a brand new, cloud-based accounting platform that handles everything for you.
• Retaining: You decide some very specialized, highly regulated documents or a unique, custom-built machine must stay in your old physical office building due to strict rules.
• Retiring: Before moving, you go through all your old files and furniture and throw away or shred anything you no longer use or need, ensuring you don't move clutter.

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Common Applications (When to Use Which Strategy):

• Rehosting: Ideal for rapid data center exits, or when an application's architecture is complex and a quick move is prioritized.
• Replatforming: Good for gaining some cloud benefits (e.g., managed databases) without a full re-architecture, balancing effort and optimization.
• Refactoring: Best for applications where agility, extreme scalability, or significant cost optimization are critical business drivers, and a fundamental redesign is justified.
• Repurchasing: Suitable when a suitable SaaS solution exists that meets business needs and can replace an existing application entirely, reducing operational burden.
• Retaining: For applications with insurmountable migration challenges (e.g., strict legal mandates, unique hardware dependencies, or very low ROI on migration).
• Retiring: A fundamental step in any migration assessment to clean up and avoid unnecessary cloud costs.

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Quick Note: The "Strategic Choice"

• The "6 Rs" are not just technical methods; they are strategic business choices.
• Understanding which "R" is appropriate for each application in an organization's portfolio is key to a successful, cost-effective, and impactful cloud migration.
• For the exam, remember the names and core concepts of each of the 6 Rs.