Cloud computing is Internet-based computing, whereby shared resources, software and information are provided to computers and other devices on-demand, like a public utility.It is a virtual computing service that is hosted on the internet.
The concept of cloud computing was introduced by Amazon.
So this a great change from client-server model.Details are abstracted from the user.All the things like server selection(what configuration ie.processor and RAM),the storage ie. Hdd capacity and other peripheral if required or not can be handled through mere API calls.It becomes easy for the user to manage the virtual server.The other facilities also include OS selection,relocation of virtual server just like a file transfer.Even addition of devices is possible by mere API calls at users end.The EC2 service provided by amazon is not free but this innovative technique saves you the cost of managing big server towers & other infrastructural costs.
For eg. Some of the hypothetical API calls could be:-
1>selectos(linux/XP);(Preinstalled OS with requisite tools can be selected or a fresh install can be made).
By these kind of calls only a server can be setup.The cost of this kind of model is cheaper than the traditional one.
The service provided by amazon is a pre-paid service.You should pay according to the facilities you want and only pay for the amount of resources you use.
Cloud computing sample architecture
Cloud architecture, the systems architecture of the software systems involved in the delivery of cloud computing, typically involves multiple cloud components communicating with each other over application programming interfaces, usually web services. This resembles the Unix philosophy of having multiple programs each doing one thing well and working together over universal interfaces. Complexity is controlled and the resulting systems are more manageable than their monolithic counterparts.
Amazon played a key role in the development of cloud computing by modernizing their data centers after the dot-com bubble, which, like most computer networks, were using as little as 10% of their capacity at any one time just to leave room for occasional spikes. Having found that the new cloud architecture resulted in significant internal efficiency improvements whereby small, fast-moving "two-pizza teams" could add new features faster and easier, Amazon started providing access to their systems through Amazon Web Services on a utility computing basis in 2006.
Nowadays,the term cloud computing is not new.Many companies like google,IBM, Microsoft have already started their research projects on cloud computing.Many OS like Ubuntu are providing features that support cloud computing.Many Vendors other than amazon have come up and are providing features like website hosting,Microsoft Exchange Services,online backup solutions,virtual hosted servers etc.
Apart from Amazon, GoGrid also allows you to choose servers and lets you create on-the-fly instances of both Windows servers and Linux servers.But isnt free.But good news is that one vendor ie. Cloud provides free as well as paid services.In free service you cant get to choose between type of OS and you get premium server services and neither have the option of installing more applications.You just get the linux based cloud having 3GB of cloud storage with standard packages installed like browser,rss feed reader,messenger etc.So you can definitely get some taste of the cloud services at http://icloud.com