  Cloud computing is a particular implementation of distributed computing. It
inherited many properties of distributed computing such as scalability,
reliability and distribution transparency. The transparency middle layer
abstracts the underlying platform away from the end user. Virtualization
technology is the foundation of Cloud computing. Virtual machine provides
abstraction of the physical server resources and securely isolates different
users in multi-tenant environment. To the Cloud services consumer, all the
computing power and resources are accessed through high speed internet access
by client platforms. This eliminates the cost to build and maintain local data
center. Resource pooling and rapid elasticity are the main characters of Cloud
computing. The scalability of Cloud computing comes from resources which can
span multiple data centers and geographic regions. There is virtually no
limitation on the amount of resources available from Cloud. New processing and
storage resources can be added into the Cloud resource pool seamlessly.
