Businesses find themselves in a tough spot when it comes to application migration to the cloud. Several complicated decisions come into play when it comes to an organization’s requirements, evaluation criteria, and architecture principles. In this context, the following cloud application migration strategies
- Rehost: Gartner’s first cloud migration guideline is that organizations re-deploy applications to a different hardware environment, and change the application’s infrastructure configuration. Application migration to the cloud becomes a faster process while rehosting, if there are no changes to the application’s infrastructure. Infrastructure as a service (IaaS) offers a key advantage, since teams can quickly migrate systems without architecture modifications. This capability could become a disadvantage due to loss of scalability benefits from the infrastructure’s cloud characteristics.
- Refactor: It refers to running applications on a cloud provider’s infrastructure. Gartner believes that the primary need for cloud application migration is the “backward-compatible” platform as a service (PaaS). This is a perfect combination of familiarity with innovation — developers can reuse investments in languages, frameworks, and containers, thus leveraging the organization’s strategic code. Refactoring has its drawbacks such as missing capabilities, transitive risk, and framework lock-in. Since the PaaS market is in its nascent stages, developers could miss several capabilities present in existing platforms.
- Revise: According to Gartner, an important cloud application migration strategy is to first support legacy modernization requirements by modifying or extending existing code base, followed by use of rehost or refactor options for deployment to the cloud. This option will help optimization of applications to bring it on par with the providers' cloud infrastructure characteristics. The downside is that starting a development project could prove expensive. According to its extent, revision probably may take the longest to deliver effective cloud application capabilities.
- Rebuild: Another important cloud application migration strategy is to rebuild the solution on PaaS, remove existing code, and totally re-architect the application. Rebuilding has its perks and drawbacks. While on one hand it requires use of new code and frameworks, it also opens the consumer to innovative features in the cloud service provider's platform. This can improve developer productivity, such as tools that allow application templates and data models to be customized, metadata-driven engines, and communities that supply pre-built components.
One of the major issues of rebuilding is lock–in. In case of unacceptable pricing or technical changes made by the provider, service level agreement breaches, or fails, the organization is forced to switch to another provider. This could mean loss of all or at least a few application assets.
- Replace – The final ‘R’ in cloud application migration strategy proposed by Gartner is replacing, which means substitution of an existing application with commercial software delivered as a service. Doing so eliminates expenditure incurred to mobilize a development team in case the requirements of business functions’ change. Replacing has its own shortcomings such as inconsistent data semantics, data access issues, and vendor lock-in.
Cloud application migration isn’t an easy decision. It bears a direct effect on various other components in the organization. Any cloud migration decision is a result of the need for an application or infrastructure modernization. Application portfolio management and infrastructure portfolio management programs should be considered while opting for cloud application migration. Optimization is the key factor of any cloud migration decision.
About the author: Richard Watson is a research director at Gartner.
(This tip is a compilation from a recent Gartner announcement.)
This was first published in May 2011