We talk of the cloud, but do we talk about the same thing? The Economist has a good piece on definitions and measurements.
The “cloud of clouds” has three distinct layers. The outer one, called “software as a service” (SaaS, pronounced sarse), includes web-based applications such as Gmail, Google’s e-mail service, and Salesforce.com, which helps firms keep track of their customers. This layer is by far the easiest to gauge. Many SaaS firms have been around for some time and only offer such services. In a new study Forrester Research, a consultancy, estimates that these services generated sales of $11.7 billion in 2010.
Going one level deeper, there is “platform as a service” (PaaS, pronounced parse), which means an operating system living in the cloud. Such services allow developers to write applications for the web and mobile devices. Offered by Google, Salesforce.com and Microsoft, this market is also fairly easy to measure, since there are only a few providers and their offerings have not really taken off yet. Forrester puts revenues at a mere $311m.
The most interesting layer—the only one that really deserves to be called “cloud computing”, say purists—is “infrastructure as a service” (IaaS, pronounced eye-arse). IaaS offers basic computing services, from number crunching to data storage, which customers can combine to build highly adaptable computer systems. The market leaders are GoGrid, Rackspace and Amazon Web Services, the computing arm of the online retailer, which made headlines for kicking WikiLeaks off its servers.