What is Virtualization

Virtualization is a technology that is changing the IT deployment and the way that people use servers. Current powerful computer hardware was designed to run a single operating system and a single application. However, this leaves most machines vastly underutilized. Each virtual machines can run different operating systems and multiple applications on the same physical computer. Virtualization technology can lets you run multiple virtual machines on a single physical machine, and sharing the resources of that single computer across multiple platforms.
In the market, we can find two major branches of products: Microsoft Virtualization with Hyper-V, and VMware Virtualization.
VMware products provides a virtualized set of hardware to the guest OS. The hardware includes video adapters, network adapters, and hard drive adapters. The virtual host can also provides pass-through drivers for guest USB, serial, and parallel devices. The virtual machines become highly portable between computers, because every host looks identical to the guests OS. A systems administrator can pause operations on a virtual machine guest, move or copy that guest OS to another physical computer, and there resume execution exactly at the point of suspension. VMotion product allows the virtual host to move a running virtual machine from one virtual host to another.
Microsoft Hyper-V is also called as Windows Server Virtualization, is a hypervisor-based virtualization system for x86 64bits systems. In Hyper-V, a partition is a logical unit which is supported by the hypervisor.
A hypervisor instance has to have at least one parent partition, running Windows Server 2008. The virtualization stack runs in the parent partition and has direct access to the hardware devices. The parent partition then creates the child partitions which host the guest OSs. A child partition can also spawn further child partitions of their own. A parent partition creates child partitions using the hypercall API, which is the application programming interface exposed by Hyper-V.
Child partitions do not have direct access to hardware resources, but instead have a virtual device. Any request to the virtual devices is redirected via the VMBus to the devices in the parent partition, which will manage the requests.