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VMWare was the first manufacturer which allowed virtualization on an Intel-platform. By using virtualization, more virtual machines (VMs) can be run on the same physical machine. It is also possible to run different operating systems at once.

This approach has a few advantages:

- Because a virtual machines consist of only files, it is easy to replace the virtual machines. It is also easier to make a complete back-up of a virtual machine.
- Virtual machines work like normal servers; the operating system on a virtual machine doesnt know it is running virtually.
- Virtual machines are independent from physical hardware changes. Changes in the physical server do not influence the virtual machine.
- Testers can test software and other things on different operating systems, while they only need one machine.

As there are advantages, VMWare also has its disadvantages.

While vmware has great advantages it is not without its drawbacks. The host-computer, used as the running virtual machine, loses a lot of its ability. The memory and the processor are shared between the two systems. The prestations are lower than when the operating system is running on a physical computer. The impact of the prestations depends on the chosen platform. ESX, for example, has some 2-5% overhead, but VMWare GSX (today better known as VMWare Server) and VMWare Workstation have some 15-25% overhead.

Workstation, GSX and ESX

The products Workstation, Server and ESX make it possible to create and run virtual machines.

The Workstation is built as a productivity tool, while Server and ESX are made for server consolidation. This consists that more physical servers are virtualized and running on a fysical VMWare Server/ESX-server. VMWare Server runs in a so-called hosted environment, which means that VMWare Server is installed on Windows or Linux. ESX on the other hand, has his own kernel (VMKernel), and thus his own operating system. This means that ESX has complete control over the hardware, which provides some advantages for tuning and prestations.

Both VMWare Server and ESX 3i are free to use. Both versions are downloadable from the VMWare website.

Virtual Center and VMotion

Virtual Center gives the possibility to manage the virtual infrastructure. A part of Virtual Center is VMotion: this is a technique to replace a virtual machine from one physical server to another, without turning off the virtual machine.

More information

Official VMWare Website
VMWARE User Group Belgium