How Server Virtualization Works on Mac Hardware and OS X

How Server Virtualization Works on Mac Hardware and OS X

Macs are the only computers that allow you to run Mac OS X Lion Server (or any flavor of OS X) with Windows and Linux. Virtualization devices on non-Apple computers cannot run Mac OS X. Apple does not allow Mac OS X to run on non-Apple devices in its End User License Agreement, so virtualization software makers do not enable it.
Imagine that your Mac is running two virtual machines – Lion Server and Windows 7. Both are running on a Mac OS X host. In each virtual machine window, you can control that operating system as you normally would by launching applications, configuring settings, and accessing the Internet.
When a virtual machine is a server, users on the network access it as they would any other server. If multiple virtual machines are running on a Mac server, users see each as a separate server.
For the latest news, tips, and troubleshooting information about running virtual machines on Macs, visit MacWindows.
With virtualization, there is one host operating system (OS) and one or more guest operating systems. The host operating system (for example, Mac OS X or Mac OS X Server) boots the real computer. On a Mac, the guest operating system can be Mac OS X, Windows, Linux, or Unix.
Each guest OS runs in a virtual machine, which is a kind of virtual reality for the guest OS. The guest OS thinks it’s running on a real PC. Although there are real hardware behind the scenes, the guest OS has no direct control over the hard drive, graphics, and other hardware: these parts of the hardware are simulated in the virtual machine.
For example, a virtual machine’s hard drive (the boot drive) is actually a file on the host Mac. This file can be up to tens of gigabytes in size, and contains the complete guest operating system, applications, settings, and documents.

The virtual hard drive file is stored on the Mac’s real hard drive, but the guest operating system does not control the entire drive. Virtualization software creates the virtual machine and maintains the guest operating system’s belief that it lives in a real computer – a bit like The Matrix, but without Keanu Reeves.
Another type of virtualization software that runs directly on “bare metal”, which means that it does not use a host operating system. To image it, remove the Mac OS X host and Mac applications. Getting rid of the host operating system reduces complexity, uses less RAM, and uses less processing power.