Virtualization is the ability to run using special software (virtual machine manager, typical examples - VMWare Workstation, Parallels Workstation, Oracle VirtualBox, one or more operating systems, called the guest and also called host system, and the operating systems can be different ( For example - Windows 7 from under Mac OS X or Windows XP from under Windows 7) or run several operating systems on the same computer at the same time using a special hypervisor program (Examples - VMWare ESXi, Xen, Microsoft Hyper-V).
Usually, virtualization is used for one of the following tasks
- Launching a guest operating system to run application software that does not work under a host system.
- Development and debugging of network and cross-platform applications on one computer.
- Running multiple instances of server operating systems on a single physical server to provide greater flexibility and security in the work (especially for web-servers).
- Facilitation of migration from one physical platform to another. (No need to reinstall OS and software, just copy the image of the virtual machine).
- To accelerate (or, in many cases, general possibilities) the work of guest operating systems, there are hardware supports for virtualization technology from processors:
VT-x (Intel Virtualization Technology) is a technology for hardware support for virtualization in Intel processors, which has now extended to almost all models of server and desktop processors: List of Intel processors with VT-x support.
AMD-V (AMD Virtualization Technology) is a technology of hardware support for virtualization in AMD processors, functionally similar to VT-x technology, but implemented in a slightly different way, therefore, in any virtualization software, support for these technologies can be present in various combinations.
VT-d (Intel Virtualization Technology for Directed I / O) is an I / O virtualization technology that allows guest machines to directly use devices such as network adapters, graphics and disk controllers. A similar AMD technology being developed is called AMD-vi