The 7 R’s strategies for migrating workloads to AWS

The 7R methodology for the migration to AWS is a framework that helps organisations plan and execute a successful migration. The methodology involves assessing each application in your portfolio and categorising it based on its suitability for migration. The outcome is an important component of the business case. Furthermore, it is the basis for detailing the migration plan.

The seven R’s stand for Retain, Relocate, Rehost, Replatform, Repurchase, Refactor and Retire.

The framework was introduced in 2016, in the most read AWS Enterprise Strategy blog post of all time (‘6 Strategies for Migrating Applications to the Cloud‘). The launch of ‘VMWare Cloud for AWS’ in 2017, added a 7th strategy.


We shall take the example of a hospital on-premises infrastructure and show how the various workloads can be treated in a real use case:

Retain — do nothing (for now and revisit later)

This involves retaining the application in its current environment and not migrating it to AWS. This may be appropriate for applications that are too costly to migrate or need to remain on premise due to latency constraints.

In the case of the hospital, some applications control Biomedical Instrumentation Technology (CT scanners, pumps, intensive care systems etc.) and need to remain on premises. These applications will be hosted on AWS Outposts to provide uniformity and ease of management (single pane of glass).

Relocate — change DC (and manage as before)

With the arrival of VMWare Cloud for AWS, VMs can be relocated to AWS without changing anything in the way they are managed.

In the case of the hospital, there was no need to retain VMWare and this option was unused.

Rehost — also known as 'lift-and-shift'

This involves migrating an application from its current environment to AWS without any modification (‘lifting and shifting ‘). It is often the simplest way to migrate. However, it does not take advantage of the many AWS services that provide the benefits of (public) cloud. As a result, it may also not optimise costs and therefore could be important to take into account a further post-migration optimisation phase, when building the business case.

In the case of the hospital, 314 VM’s (mostly application servers) could be migrated in this manner.

Replatform — also known as 'lift-tinker-and-shift'

This involves making minor changes to the application to take advantage of some AWS services while retaining the core architecture. This approach can provide some benefits of cloud-native services while minimising the risk and effort of a full refactor.

In the case of the hospital, 50 VMs running the backups, file servers, System Center Operations Manager, Security software were replaced by Platform as a Service (PaaS) offerings at AWS. In addition, all VMs used for Citrix could be replaced by Desktop as a Service AWS offerings.

Repurchase — move to a different product

This involves replacing the existing application with a cloud-native software as a service (SaaS) application. It can reduce the operational overhead of managing the application and provide more agility. However, it may require changes to business processes and training the end-users.

At the hospital, 29 VMs running applications could be replaced by alternatives that were offered as SaaS solutions.

Refactor — re-architect using cloud-native features and services

This involves rebuilding an application using modern cloud-native architecture patterns or moving to a cloud native solution provided by AWS. It can provide the most benefits but is the most time-consuming and requires significant investment. If the migration needs to happen fast, this strategy is often applied in a second phase after a first, much faster rehosting phase.

The hospital decided that the traditional SQL server based data warehouse would be moved to a cloud native AWS data lake with corresponding serverless services such as Amazon Glue, Amazon Athena and Amazon Quicksight.

Retire — stop using and get rid of

This involves retiring applications that are no longer needed or have low business value. It can reduce the complexity of the migration and ongoing management costs. Quite often the on-premises environment contains VMs and applications that qualify for this scenario. After all, a significant portion of the costs are fixed and sunk. However, it pays off to clean up before a migration: you save on the migration effort and avoid paying for what you deploy in the cloud.

The hospital identified 128 VMs that did not need to be migrated and could be retired.

Cambrian uses the 7R methodology to help organisations prioritise which applications to migrate first, determine the appropriate migration strategy, and manage the risks associated with migration. We carefully evaluate each application in your portfolio and choose the migration strategy that best meets your business needs.

Are you interested to discover how we can help you assess your portfolio and design a migration strategy balancing speed, cost and risk? Get in touch and send us a message.

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