When people talk about Virtualisation, they’re usually referring to either Server, Desktop or Application virtualization. Server Virtualisation means partitioning one physical server into several virtual servers, or machines. Each virtual machine can interact independently with other devices, applications, data and users as though it were a separate physical resource.
Different virtual machines can run different operating systems (OS) and multiple applications while sharing the resources of a single physical computer. And, because each virtual machine is isolated from other virtualized machines, if one crashes, it doesn’t affect the others.
Hypervisor software such as VMware ESX/ ESXi, Citrix Xenserver or Microsoft Hyper-V are the secret sauce that make virtualisation possible. This software, also known as a virtualization manager, sits between the hardware and the OS, and decouples the operating system and applications from the hardware. The hypervisor assigns the amount of access that the operating systems and applications have with the processor and other hardware resources, such as memory and disk input/output.
In addition to using virtualisation technology to partition one machine into several virtual machines, you can also use virtualization solutions to combine multiple physical resources into a single virtual resource. A good example of this is storage virtualization, where multiple network storage resources are pooled into what appears as a single storage device for easier and more efficient management of these resources.