Migration to the cloud is a very important topic for IT departments but also for the business areas and the companies as a whole. All stakeholders need help to make decisions when deciding how to migrate applications based on business requirements, costs and technology to the cloud. That cloud can be any of the currently available, considering IaaS, PaaS and SaaS services.
By 2011, Gartner stated 5 R’s for migration to cloud. Then a new R was added and the final model become The 6 R’s for migration to the cloud.
The 6 R’s
This section describes the options for migration of existing applications to the cloud. Six different strategies are applicable.
- Rehost (“lift and shift”)
- Replatform (“lift, tinker and shift”)
- Repurchase (“drop and shop”)
- Refactor / Re-architect
- Retain / Re-visit
1. Rehost (“lift and shift”)
Move applications without changes. In large scale, legacy migrations, organizations are looking to move quickly to meet business objectives. The majority of these applications are re-hosted. GE Oil & Gas found that, even without implementing any cloud optimizations, it could save roughly 30 percent of its costs by re-hosting. Most re-hosting can be automated with tools. Some organizations prefer to do this manually as they learn how to apply their legacy systems to the new cloud platform. Applications are easier to optimize/re-architect once they’re already running in the cloud. Partly because the organization will have developed the skills to do so, and partly because the hard part—migrating the application, data, and traffic—has already been done.
2. Replatform (“lift, tinker and shift”)
Make a few cloud optimizations to achieve a tangible benefit. You will not change the core architecture of the application. For example, reduce the amount of time you spend managing database instances by migrating to a database-as-a-service platform, or migrating your application to a fully managed platform. A large media company migrated hundreds of web servers it ran on-premises to the cloud, and, in the process, it moved from WebLogic (a Java application container that requires an expensive license) to Apache Tomcat, an open-source equivalent. This media company saved millions in licensing costs on top of the savings and agility it gained by migrating to the cloud.
3. Repurchase (“drop and shop”)
Move from perpetual licenses to a software as a service. For example, moving a CRM to Salesforce.com, an HR system to Workday, or a CMS to Drupal.
4. Refactor / Re-architect
Re-imagine how the application is architected and developed, using cloud-native features. This is driven by a strong business need to add features, scale, or performance that would otherwise be difficult to achieve in the application’s existing environment. Are we looking to migrate from a monolithic architecture to a service-oriented (or server-less) architecture to boost agility or improve business continuity? This strategy tends to be the most expensive, but, if we have a good product-market fit, it can also be the most beneficial.
Remove applications that are no longer needed. Once you have completed discovery for your environment, you will ask who owns each application. As much as 10%-20% of an enterprise IT portfolio is no longer useful, and can simply be turned off. These savings can boost the business case, direct your team’s attention to the applications people use, and reduce how many applications you have to secure.
6. Retain / Re-visit
Keep applications that are critical for the business, but will require major refactoring before they can be migrated. All applications that fall in this category can be revisited at later point in time.
The journey to the cloud has to be structured in order to successfully guarantee the business continuity. All the cloud services must be evaluated to take advantage of the capabilites available on the destination platform and a roadmap should be designed, going from current to future state.
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 Gartner, Gartner Identifies Five Ways to Migrate Applications to the Cloud, 2011.
 Amazon, Migrating to Amazon Web Services, 2017.