Rehost migration strategy, commonly known as 'lift and shift,' is one of the fundamental approaches in AWS migration methodologies. This strategy involves moving applications from on-premises infrastructure to AWS cloud with minimal or no modifications to the existing architecture or code base.
In…Rehost migration strategy, commonly known as 'lift and shift,' is one of the fundamental approaches in AWS migration methodologies. This strategy involves moving applications from on-premises infrastructure to AWS cloud with minimal or no modifications to the existing architecture or code base.
In a rehost scenario, organizations replicate their current environment in AWS, maintaining the same operating systems, middleware, and application configurations. This approach leverages services like AWS Application Migration Service (AWS MGN), which automates the conversion of source servers to run natively on AWS infrastructure.
Key benefits of the rehost strategy include rapid migration timelines, reduced complexity, and lower initial risk compared to more transformative approaches. Organizations can typically achieve migrations within weeks rather than months, making it ideal for time-sensitive projects or when meeting datacenter exit deadlines.
The rehost approach works particularly well for legacy applications where source code access is limited, applications with complex dependencies that are difficult to decouple, or situations where the primary goal is quick cloud adoption before optimization. Many organizations use rehost as a stepping stone, migrating first and then modernizing applications once they operate in the cloud environment.
AWS provides several tools supporting rehost migrations. AWS MGN offers continuous block-level replication, ensuring minimal cutover windows. CloudEndure Migration provides similar capabilities for large-scale migrations. AWS Server Migration Service (SMS) supports incremental replication of on-premises VMware vSphere, Microsoft Hyper-V, and Azure virtual machines.
While rehost provides speed advantages, organizations should understand that this strategy may not fully leverage cloud-native benefits such as elasticity, managed services, or serverless architectures. Cost optimization opportunities might be limited initially since the architecture remains unchanged. However, once migrated, teams can gradually refactor and optimize workloads to take advantage of AWS cloud capabilities, making rehost an effective first step in comprehensive cloud transformation journeys.
Rehost Migration Strategy (Lift and Shift)
What is Rehost Migration Strategy?
Rehost, commonly known as lift and shift, is a migration strategy where applications are moved from on-premises infrastructure to the cloud with minimal or no changes to the application architecture. The application is essentially 'lifted' from its current environment and 'shifted' to AWS infrastructure in its existing state.
Why is Rehost Important?
Rehost is one of the most frequently used migration strategies because it offers several key advantages:
• Speed: Fastest path to cloud migration, enabling organizations to meet tight deadlines • Lower Risk: Minimal changes mean fewer opportunities for introducing bugs or failures • Cost Savings: Organizations can begin realizing cloud benefits such as reduced data center costs quickly • Foundation for Future Optimization: Once in the cloud, applications can be optimized incrementally • Skill Requirements: Requires less cloud-native expertise compared to refactoring approaches
How Rehost Works
The rehost process typically involves these steps:
1. Discovery and Assessment: Use AWS Application Discovery Service or Migration Evaluator to inventory existing workloads
2. Migration Planning: Create migration waves and prioritize applications based on dependencies and business criticality
3. Server Replication: Use AWS Application Migration Service (AWS MGN) to replicate servers to AWS. This tool performs continuous block-level replication
4. Testing: Launch test instances in AWS to validate functionality before cutover
5. Cutover: Perform the final migration during a maintenance window, redirecting traffic to AWS resources
Key AWS Services for Rehost
• AWS Application Migration Service (MGN): The primary service for lift and shift migrations, supporting both physical and virtual servers • AWS Database Migration Service (DMS): For migrating databases with minimal downtime • AWS Migration Hub: Central location to track migration progress across multiple AWS tools • CloudEndure Migration: Legacy tool now integrated into AWS MGN
When to Choose Rehost
Rehost is ideal when: • You need to migrate quickly to exit a data center • Applications are stable and do not require architectural changes • You want to reduce technical debt before optimization • Budget or time constraints prevent more complex migrations • Applications are difficult to modify due to legacy code or lack of expertise
Limitations of Rehost
• Does not take full advantage of cloud-native features • May result in higher operational costs compared to optimized architectures • Technical debt is carried forward to the cloud environment • Scalability may be limited by original application design
Exam Tips: Answering Questions on Rehost Migration Strategy
• Recognize Scenario Keywords: Look for phrases like 'minimal changes,' 'fastest migration,' 'as-is migration,' 'lift and shift,' or 'tight timeline'
• Understand Tool Selection: AWS MGN is the recommended service for rehosting. If you see CloudEndure mentioned, understand it has been succeeded by MGN
• Differentiate from Other Strategies: Know that replatform involves some optimization, while refactor involves significant architectural changes. Rehost means keeping the application unchanged
• Consider Business Drivers: When questions mention data center lease expiration, cost reduction urgency, or migration deadlines, rehost is often the answer
• Post-Migration Optimization: Remember that rehost can be followed by optimization phases - this is a valid long-term strategy
• Licensing Considerations: Be aware that some questions may address bring-your-own-license (BYOL) scenarios, which are common with rehost
• Downtime Requirements: AWS MGN supports near-zero downtime migrations through continuous replication - this is often tested
• Compare with Retain or Retire: If an application should not be migrated at all, retain (keep on-premises) or retire (decommission) may be better choices than rehost