Cloud computing is a new way of using resources (particularly hardware, software) in IT, based on the possibility of sharing between applications and to eliminate direct links to the actual application logic components (virtualization).
Because to make better use of infrastructure purchased or even run applications on the infrastructure of "borrowed" from a distance. It also unifies and simplifies management to the level of self-service for users where possible.
Since the development of virtualization technologies, together with high bandwidth local area networks and the Internet to take advantage of cloud computing concepts in a real environment. General economic development also makes for massive savings can be reached with the help of cloud computing.
The cloud we're talking when virtualization environment has reached a certain critical value (about 75% of all servers), which are beginning to discover the benefits of consistency management and resource allocation. Cloud computing is not possible without virtualization, not just in servers but also in networking and storage.
1) The gradual building of the private cloud, internally in the company environment.
2) Convert any application into the environment of the cloud providers (public cloud).
3) The combination of the above approaches - building a private cloud with the possibility of occasional use (or longer for selected applications) external sources (hybrid cloud).
Number of services at the application level (free e-mail, online storage, maps, etc..) Can be considered a "cloud" because it can be used remotely through APIs or specialized clients. Likewise, providers who already provide hosting virtual machines on which applications are installed on the customer.
Thus, no dedicated infrastructure, a large number of commodity hardware? You can. But you have a similar structure of the application. Thus, a relatively small number of applications which have a relatively large control (developing them yourself). If you are in a "normal" conditions and you must run the database, e-mail, ERP systems, etc., be gone before you to build a "normal" way.
Cloud is not just about technology. It is primarily a change in the logic of understanding of IT resources. It is not easy to break ties experienced a "My application runs on server" A ", which is on the second floor of the 105th in the room." Sharing resources is a concept that saves money, but met with resistance "owners". It's always something better psychologically "own" rather than "share".