Virtualization has been widely embraced for its ability to rein in costs, lower TCO, and get higher utilization out of IT resources. To date, IT organizations have focused on how to scale-up virtualization on a single server. That is, the focus has been how to run more virtual machines on one machine. Increasingly, the attention today is shifting to how to scale-out efforts where virtual machines and virtual instances of applications are distributed across multiple servers. This, in essence, creates an internal cloud that allows companies to virtualize IT services throughout an enterprise.
Cloud Computing 
