VirtualMachines

Virtual machines (VMs) are methods which allow to divide computer resources in order to provide further, only virtually existing resources. The hardware's physical reality is hidden, the required hardware is only simulated by the software.
Virtual machines (VMs) provide either a virtual server (host-system) or a virtual runtime environment for programmes within a host-system.

Possible usages

VMs are often used, if separate operating system environments are necessary for applications which need little or only temporarily computing power (like e. g. charge reports of telephone systems). Furthermore VMs are particularly suited for out-dated software which is no longer executable on current operating systems, but which must stay utilisable (e.g. software for financial accounting).
Even in developing software different release states may be tested on different operating systems without any additional hardware. The easy passing on of files by copying them makes the technical support also easier.

Advantages

VMs consolidate physical systems on servers  (server consolidation) and thus offer the following advantages:

• Low costs for hardware aquisition and maintenance
• Low-priced and standardised production environment
• Faster and cheaper disaster recovery
• Central management of all virtual machines and central monitoring of server systems