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Although a young technology, server virtual technology is currently the main issue in information technology. Server virtual technology is a process that allows a server administrator to mask server resources from server users. The resources may include processors and operating systems. The administrator uses a software application to divide a single server into several isolated virtual environments or virtual private servers. The creation of virtual servers has traditionally used special software that tricks a server’s CPU into powering virtual machines. This is not the case anymore, as virtual servers can now be created by the use of a single processor capable for supporting virtual servers. However, software still has to be used in the creation of the virtual servers. A server administrator can achieve server virtualization through three different models: • Virtual machines model (VMM) – Virtual machines use the resources available on the main server. The virtual operating system therefore runs without any modifications. This approach allows a server administrator to create virtual servers that use different operating systems. A virtual server runs without knowledge that it runs on hardware. However, an administrator has to enable coordination between the server CPU and virtual servers. This is achieved by using a virtual machine monitor (VMM) that validates all instructions from the virtual machines to the server’s CPU. • Paravirtual machine model (PVM) – As in VMM, the PVM model also depends on main server resources and uses a virtual machine monitor. However, unlike in VMM, the virtual machine monitor in PVM modifies a virtual machine’s code (porting). Paravirtual machines can also have different operating systems. • Operating System (OS) – Virtualization at the OS level is very different from VMM and PVM models. It is from the OS that all functionalities are exported to virtual machines or Paravirtual machines. Unlike in VMM and PVM models, the OS model requires that all machines use the same OS. However, different distribution of the same OS is allowed. The different distribution makes it possible for other machines to operate, even if one machine fails. Server virtualization is very important in the development of automatic computing. It can be used in eliminating server sprawl, efficient use of main server resources, administration and in server disaster recovery. Server virtualization is now the trend in the IT industry and more possibilities and capabilities are still under consideration, including storage, network and workload management virtualization. With the use of a blade server, a high degree of efficiency at minimal cost is possible.
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