Anyone who has moved houses knows there is nothing worse than hauling boxes and boxes of stuff, only to unpack it all on the other end and discover that the beloved furniture and knick-knacks do not work in the new place. Portability is a tricky concept, and moving applications to the cloud is not much different than moving house. Just as every home is uniquely suited to certain décor pieces and not to others, every cloud requires certain specifications. The code and configurations that worked like a charm in one cloud environment suddenly look like a bull in a china shop when moved to a new cloud.

The Myth of Cloud Portability
One of the most advertised benefits of moving applications to the cloud is the so-called portability that the cloud environment offers. The claim is that enterprises can easily switch cloud jurisdictions whenever they need to scale up or add features. Portability is indeed an important factor for businesses concerned about vendor lock-in, as moving applications into a new environment can involve a lot of heavy lifting.

In reality, cloud portability is a myth, and InfoWorld's cloud computing blogger David Linthicum drove the point home in a recent blog post. "The reality is that using any technology, except the most primitive, causes some degree of dependency on that technology or its service provider. Cloud providers are no exception," Linthicum writes. "Companies that create technology have no incentive to fly in close enough formation to let you move data and code willy-nilly among their offerings and those provided by their competitors. The cloud is no different in that respect."

There is truth in Linthicum's statement. Moving applications to clouds with proprietary deployment or technology stacks often creates cross-platform issues that limit portability. In fact, when portability relies on the cloud provider, applications inevitably encounter provisioning and configuration dependencies that create vendor lock-in. Further, a new cloud provider might not have a clue how to install, deploy, run, and manage an organization's applications without detailed information about the apps and their underlying stacks.

Companies should not have to give up on portability. They need the freedom to switch cloud providers on short notice to reduce cost, enhance reliability, initiate geographic expansion, or meet compliance requirements. To make a successful move, they require the help of a moving company of sorts. Platform as a Service (PaaS) offers this much needed service to enterprises on the move.

Platform as a Service (PaaS): Global Citizen of the Cloud
As an elastic middleware layer between the applications and the cloud provider, PaaS delivers a standard open approach that simplifies the interfaces common to multiple clouds without doing away with the value-added features that make each cloud unique.

With PaaS, businesses travel light from one cloud to another. A PaaS sits between the software and the infrastructure, providing everything an application needs to run, including hardware, operating system, database, language runtime, modules, and web framework. The PaaS middleware layer removes borders and gets rid of the vendor-specific excess luggage. Applications can easily travel to a new cloud provider or to the enterprise's private cloud.

A PaaS can be deployed on multiple hypervisors and on different types of Infrastructure as a Service (IaaS) foundation. In a three-tiered cloud computing model, the PaaS middle layer lies between the application and the IaaS, enabling portability. Enterprises can painlessly push their applications to any cloud anywhere, and with little or no reengineering.

When choosing a technology stack for portability, there are several factors to consider. It is best to include a PaaS layer that is built with open standards, uses lightweight bindings, and is portable on most cloud operating platforms. Businesses either have the option of selecting a cloud-hosting provider that offers a PaaS layer or deploying their own private PaaS.

With a PaaS, cloud portability becomes real, and its simplicity will surely bring the house down. Because those moving boxes aren't going to unpack themselves.