7 Rs of Migration
Migrate applications and data from datacentres / cloud providers / regions to an equivalent cloud infrastructure of another cloud provider or region. Also referred as Switching Location or Hypervisor-Level Lift and Shift.
THE GOOD
- Minimizes downtime and disruption since users remain seamlessly connected during the migration process.
- No impact on ongoing operations, no need to rewrite the application source code, no retraining of staff or investment in upgraded hardware is required.
THE BAD
- Not able to take advantage of cloud native features (managed services, scalability, etc.) as workloads are not optimized for cloud.
- Since most of the operations are still managed by the organization, relocating does not shift much responsibility to the cloud provider to help save time and effort.
THE UGLY
- Continued maintenance and compatibility with existing applications on the new platform can use time and resources.
- Minimal benefit in terms of cost saving because of hypervisor license, operational overhead.
AWS Services and Tools: VMware Cloud on AWS, Amazon EKS
Migrate applications and data from on-premises infrastructure to the cloud without making any significant changes to the application architecture. Also referred as Lift and Shift.
THE GOOD
- Quickly migrate applications with minimal disruption "as-is" to the cloud services that match the workload's existing storage, networking, and compute requirements.
- Using rehosting, companies can increase their systems' resilience, service availability, and more without costly system upgrades.
THE BAD
- Not able to take advantage of cloud native features (managed services, scalability, optimization etc.) as workloads are not fine-tuned for cloud.
- A rehosted workload may introduce compatibility, performance, security, and other technical and operational gaps, negatively affecting end users.
THE UGLY
- By rehosting, an application becomes cloud-enabled and cloud-based, not cloud-native. As a result, the workload is still restricted in utilizing cloud-native capabilities.
- The migration process may fail if the application requirements aren't mapped out accurately to the corresponding cloud configuration.
AWS Services and Tools: AWS Application Migration Service, Amazon EC2, AWS Elastic Beanstalk
Replatform strategy modifies existing on-premises applications to work optimally in the cloud while retaining much of their core architecture. Also referred as Lift, Tinker (modify) and Shift.
THE GOOD
- It mostly involves switching from self-hosted architecture to managed services.
- It allows applications to leverage cloud capabilities, like auto-scaling, managed storage, automation and data processing services.
THE BAD
- Even if it requires only minor changes, making the changes can still be costly and time-consuming compared to rehosting.
- It requires thorough testing, continuous AWS monitoring, and anomaly detection to avoid costly issues.
THE UGLY
- Sometimes "scope creep" can turn a replatform project to refactor project.
AWS Services and Tools: AWS Database Migration Service, AWS Application Migration Service
Refactoring helps break down a monolithic application into microservices to achieve high availability and enhanced levels of automation. Also referred as Redesign or Rearchitect.
THE GOOD
- High ROI due to scalability, reducing consumption of resources (and therefore costs) by aligning the cloud infrastructure with the requirements.
- The most future-proof migration approach.
THE BAD
- The process requires thorough planning, execution, and testing to prevent errors from causing cloud security, performance, and cost problems.
- Applications can partially become locked into certain public cloud providers due to reliance upon cloud-native features.
THE UGLY
- Often considered the most complex migration option as executing it takes the most time, effort, and money.
- Extensive planning, training, cloud expertise is required for refactoring.
AWS Services and Tools: AWS Migration Hub Refactor Spaces
Repurchasing aims to replace legacy systems and move to a consumption-based, SaaS subscription in cloud leveraging cloud-native capabilities. Also referred as Drop and Shop.
THE GOOD
- Adopt a cloud-optimized solution quickly and reduce migration costs drastically.
- Leverage the advantages of a proven solution without the need for extensive development efforts.
THE BAD
- There's nothing you can do about service outages other than wait for a fix.
- Often, you cannot make significant changes to the platform because someone else owns it.
- You may have to train your team and users with the new system.
THE UGLY
- You have to wait for the SaaS provider to release updates at their own pace to fix security, compatibility, and performance issues.
AWS Services and Tools: AWS Marketplace
Retire is a cloud migration strategy option where we turn off services that are redundant or legacy and no longer in use or needed. Also referred as decommissioning or archiving.
THE GOOD
- The passive migration strategy requires the least funds, time, unique expertise, and effort.
- Reduces expenditure on idle resources by retiring enables the organization to focus on areas that provide more business value and saves resources.
THE BAD
- A careful analysis is required to ensure that retiring any component does not adversely impact other business processes.
- You must be aware of all the upstream dependencies of a workload before retiring them.
THE UGLY
- Deciding if applications should be retired can often become complex and involves a level of risk. This can result in action being postponed, especially if subject matter experts (SMEs) have left an organization.
- Also, documentation about legacy systems can be sparse.
AWS Services and Tools: Does not apply
Retain certain applications on-premises while migrating others to the cloud with a plan to revisit them later for further decision-making. Also referred as revisit, reassess or co-locate to a service provider.
THE GOOD
- Allows for evaluation of (recently upgraded) applications in order to identify those that require immediate migration or those that could be migrated in the future.
- Saves cloud resources by retaining inefficiencies on-premises.
THE BAD
- The longer you keep the workload on-premises, the more resources you may waste supporting it.
- Maintaining the status quo may mean not exploring more efficient, secure, cost-effective, and productive practices in a new environment.
THE UGLY
- Lack of cloud-native capabilities, meaning no automated scaling or improved performance.
- Requires costly and continuous maintenance of the on-premises hardware.
AWS Services and Tools: Does not apply