ABSTRACT
Peng Liu, a Chinese expert in grid computing and cloud computing, defines cloud computing as follows: cloud computing distributes computational task in the resource pool constituted by a large number of computers so that various application systems are able to obtain computing power, storage space and all kinds of software services as needed. Simply speaking, cloud computing is to establish a huge computational system by a large-scale data center and a super computer cluster so that users can acquire various kinds of software and services through the internet instead of buying an independent operating system and various software for each computer[1].
