It is the most hot topic in the IT industry currently.Your program is divided into many parts. The part that you interact with (UI) is stored in your computer but the part that does essential processing is stored in servers somewhere else. UI in turn interacts with part(s) on server. The part(s) stored somewhere else (servers) form(s) a cloud because you don't worry about how the processing is being implemented on the sever. You have to only worry about your essential data being passed and stored in the servers if those servers belong to someone else (Companies).What you are using right now is on cloud.
Imagine you need to share a lot of videos on a website and with limited storing capacity you share some videos on other server in your network. Which may be at geographically different location but is in your network.(Search Google for VPNs).The user when watches the videos is not aware of the fact that the video he is watching the video is present coming from a server which is in a geographically different location than where the website is.
You may be authenticated to use a website but you may not be authorized to change the content which a website admin can do. So security is the headache to some extent how the application has been developed.
Now take a different scenario,
You can see a practical example railways website. You have a server running which is serving millions of transactions per second .If one of the server becomes busy then the transaction should not fail the application should be intelligent enough to communicate on another server which is free i.e. can handle that request and perform same changes to databases which has been requested at booking counter. If you do not have a cloud of servers running you will not be able to do it fastly.
Security is responsibility of system administrators and developers who developed that system.Well very simply put, cloud computing is all about getting a software service over network and more importantly internet.There is nothing new in cloud computing as a concept, because email, web, and many other services have been available over the internet/network for many years now.
What is happening now, is
1. Internet is getting faster.
2. Computing demands of individuals are rising.
3. Consumer software keeps on getting outdated.
The paradigm shift that cloud computing provides is that an ordinary user can have an inexpensive laptop/slate computer and run applications on cloud. Using Google docs vs ms office is a typical example.
The landscape of getting services delivered over internet is huge and possibilities are innumerate. And it is one of the modern buzzword. Also there are all sorts of systems, networking, hardware and security challenges in providing cloud computing. So you find almost every company doing something or else doing with the cloud.
Lastly cloud computing has sort of become a buzz word like "dot com" used to be about 10 years back. People must understand that cloud computing is nothing new from a technology point of view. But it is a shift in how we perceive software services.
Not everything can be done over cloud and even with the advent of cloud computing traditional will still continue. What industry experts claim is that we will see a shrinking desktop market and desktops will be replaced by more mobile computers like notebooks, net books, smart phones , slate computers and smart devices like smart cam coders etc. This will be backed by increasing sizes of data centers all over the world.
Characteristics of cloud computing
Agility – On demand computing infrastructure
Reliability and fault tolerance
Self healing – Hot backups, etc
SLA driven – Policies on how quickly requests are processed
Multi-tenancy
Service-oriented
Virtualized
cost-effective
platform, location and device independency
Basically an Internet-based network is made up of large numbers of servers Contain vast amounts of information. Users only care about the service or information, not about the underlying details.
History of Cloud computing
In 1960 It was found by John McCarthy and came into commercial use around the turn of the 21st century .By, 2007 saw increased activity, including Google, IBM .It was a hot topic by mid-2008 and numerous cloud computing events had been scheduled.