Few terms have been as simultaneously hyped and reviled as "cloud computing," but there's definitely more to the phenomenon than just a buzzword and some vague talk of "efficiencies" and "agility." We've put together this short, simple introduction to cloud computing that you can send to your CIO the next time you catch him abusing "the cloud" at a meeting. There's a kind of supply-and-demand dynamic that applies to technical terms—when a few knowledgeable insiders are hoarding a word, it maintains its meaning, but when the masses get hold of it and abuse it, it's quickly emptied of value. This is certainly the case with "the cloud," a term that used to mean something, and now means everything and nothing. "The cloud" is so overused by startups desperate for VC money, and by big companies desperate to look like hip startups, that IT professionals are increasingly wary of anything cloud-related. It doesn't help that the image conjured by the word is of something vaporous, flimsy, and fleeting—whatever cloud is, it doesn't sound like the kind of thing you want to entrust critical business functions to.

Despite the fact that everyone seems to see a different shape when they stare at it, there is something worth preserving in "the cloud" as a term that usefully describes one approach to what is often called "utility computing," which latter term is itself a metaphorical way of speaking about a business model centered around the idea of computing power as a service like electrical power.

In first defining and then describing cloud computing in this brief article, my aim is to provide a useful definition for IT professionals who are tasked with exploring cloud services as a potential avenue for finding new efficiencies, reducing fixed costs, tackling scaling challenges, and solving novel problems at Internet scale. My secondary audiences for this piece are IT pros who need to quickly explain "the cloud" to a clueless CIO, and clueless CIOs who'd rather not have to rely on IT pros to explain buzzwords to them.

This article takes a historical and comparative approach to the topic of cloud computing. First, I'll introduce the venerable client-server model, a model of which cloud is just the latest instance, and then I'll contrast the cloud with its immediate predecessor, the grid. Finally, I'll describe the three-tiered model of cloud services. (Read More)