So what exactly is Cloud Computing? In short, it is applications and processes held on, and delivered from the Internet. The data that you create and use within these applications and processes is also held online and is accessible from anywhere you have an internet connection and compatible client (like a web browser). It is a varied model raging from full virtual machines running in the 'cloud' to a simple calendar app that you access from a web browser. The defining characteristic of Cloud Computing is that the application and associated data are held on the Internet somewhere, and not necessarily on one computer, but usually across a cluster of computers acting as a seamless whole.

OK, got that, but how does that relate to hosting?

Thats a good question. With cloud hosting you upload your web application and associated data (usually an SQL database of some description) to the hosting service. You application is then 'distributed' across the service in such a way that a failure on any one of their servers or networks should not be able to bring down your application. In addition, because your application is hosted on the same service as everyone else you should benefit from levels of bandwidth and processing power designed for applications which field vastly more traffic than your own. In short, you should never run out of bandwidth, processing power or storage because the hosting system is designed with vast amounts of spare capacity.

Sounds a bit like shared hosting to me!

On the surface this does sound like shared hosting but their are some critical differences. With shared hosting your website is stored on one big server along with tens and possibly hundreds of other websites run by different people. Badly coded sites on the your server can drain resources and negatively effect the performance of every site hosted on it. You are also sharing the bandwidth available to that one server.

With Cloud hosting, all websites and web apps are shared across the entire infrastructure. The service decides which sites need processing power and bandwidth dynamically by detecting how much traffic they are receiving. In this way there is always lots of spare capacity in the system and if there is a spike in traffic because your website got dugg, the service can respond dynamically in real time by adding resources as required.

Cool, sounds good, where can I sign up?

Well there are several services on the market at the moment and they vary from each other in important ways. Over the next series of articles I'm going to look at each of the big ones and give and overview of what they offer and who they seem to be best suited to. In particular I'll cover:

• Google App Engine (or GAE for short)
• Amazon's EC2 and S3
• Rackspace Cloud
• Engine Yard (Rails Hosting)

In the next part I'll take a look at Google App Engine.