Virtualisation

Virtualisation can help you do more with less. Put simply, the technology enables more than one instance of an operating system to exist within a physical machine all running simultaneously. This means that whereas you would normal expect to have a separate physical server for each function, such as email, database, webserver etc, now we can run all these functions from a single piece of hardware.

Virtualisation is accomplished via a special software kernel called a hypervisor. This allows a number of operating systems to share resources on one physical machine, thus making more efficient use of hardware resources.

VMware

VMware is the most widely used virtualisation at the moment. A suite of products is offered to allow enterprise virtualisation. These include VMware ESXi hypervisor, vmotion, HA (High availability), DRS (Dynamic Resource Scheduler) and FT (Fault Tolerance). Vmotion is a technology which allows a virtual machine to be move between physical hosts whilst running. The possibility of seemless movement allows other features used in HA, DRM where virtual machines can be moved automatically should the hardware environment change, or a machine require restarting.

Linux Kernel Virtual Machine (KVM)

By default  the Linux kernel (since kernel 2.6.20) comes with a module which allows virtualisation. This means that most 64bit  Linux computers (where processors have the VT/AMD-V extension) can immediately be used to host virtual machines.