The term “virtualisation” refers to the possibility to abstract the hardware components of an ordinary computer in order to make them available to software in the form of virtual resources.

The term “virtualisation” refers to the possibility to abstract the hardware components of an ordinary computer in order to make them available to software in the form of virtual resources.
This process allows for installing one or several different operating systems on the same server dividing it into virtual machines.
One advantage of server virtualisation is that such server has all the potentials and features of a physical server while the resources are shared by all the virtual machines.

Multitasking systems allow each virtual machine to have its own hardware logically distributed and to have its own operating system and dedicated programs, all of these being logically separated from the other virtual machines.
The transition to a lower number of servers reduces the management costs of several physical machines. The VMware technology separates software from hardware, thus making it possible to run operating systems and applications on a single computer with substantial improvements in terms of efficiency, availability, flexibility and management.

What is a hypervisor?

A hypervisor is a program for creating and running virtual machines. Hypervisors have traditionally been split into two classes: type one, or “bare metal” hypervisors that run guest virtual machines directly on a system’s hardware, essentially behaving as an operating system. Type two, or “hosted” hypervisors behave more like traditional applications that can be started and stopped like a normal program. In modern systems, this split is less prevalent, particularly with systems like KVM. KVM, short for kernel-based virtual machine, is a part of the Linux kernel that can run virtual machines directly, although you can still use a system running KVM virtual machines as a normal computer itself.

A hypervisor is a form of virtualization software used in Cloud hosting to divide and allocate the resources on various pieces of hardware. The program which provides partitioning, isolation, or abstraction is called a virtualization hypervisor. The hypervisor is a hardware virtualization technique that allows multiple guest operating systems (OS) to run on a single host system at the same time. A hypervisor is sometimes also called a virtual machine manager(VMM). 

What is a virtual machine?

A virtual machine is the emulated equivalent of a computer system that runs on top of another system. Virtual machines may have access to any number of resources: computing power, through hardware-assisted but limited access to the host machine’s CPU and memory; one or more physical or virtual disk devices for storage; a virtual or real network interface; as well as any devices such as video cards, USB devices, or other hardware that are shared with the virtual machine. If the virtual machine is stored on a virtual disk, this is often referred to as a disk image. A disk image may contain the files for a virtual machine to boot, or, it can contain any other specific storage needs.

The use of virtualization for a broad range of mission-critical applications thus contributes to:

• Reducing the TCO (Total Cost of Ownership)
• Enhancing business agility
• Simplifying the management of systems
• Enhancing energy efficiency