alization host operating software from companies such as VMware, Inc. (VMware was developed by EMC, which is now owned by Dell) and Microsoft allocate and manage computer resources such as memory, hard-disk capacity, and computer processing between the operating systems and applications on a server. Virtualization management software simplifies data center operations by providing the ability to allocate more resources in a data center from a single interface. Server sprawl can be a problem when many applications are replicated on diverse servers. It is often a challenge to manage the large number of virtual machines located within a data center. Scalability and Energy Savings Carriers, ISPs, enterprises, and developers adopt virtualization as a way to save on energy, computer memory, staffing, and hardware costs. Installing applications on multiple virtual computers on each physical server decreases the number of physical servers required. It also ensures that there is less wasted capacity than on physical servers used for a single application, often using only 10 percent of the physical server's capacity. This makes data centers more scalable. Applications can be installed more easily, without adding extra hardware. Rather, a new virtual machine can be added to a physical computer that has spare capacity www.TechnicalPDF.com until the physical server is at between 70 percent and 80 percent of capacity. In addition, having fewer computers to run applications results in less space used and lower facility cooling costs. Although individual servers running virtual operating software are more powerful and require more cooling than less-powerful servers, the reduction in the total number of physical devices results in overall energy efficiency. Virtualization-Enabling Cloud Computing Virtualization is a major enabler of cloud computing. Server virtualization refers to a single physical server with multiple operating systems and applications. Prior to server virtualization, each unique operating system required its own