Virtual Machine Monitor Execution Modes in VMware vSphere 4.0
Included in VMware vSphere 4.0 is VMware ESX 4, the newest generation of a hypervisor deployed in hundreds of thousands of production environments. All versions of ESX comprise two components: the Virtual Machine Monitor (VMM) and the kernel. The monitor is a thin layer that provides virtual x86 hardware to the overlying operating system. The virtual hardware is called a virtual machine and the operating system it runs is called the guest. It is through the monitor that the virtual machine leverages key technologies in the kernel such as memory management, scheduling, and the network and storage stacks. Prior to the introduction of hardware support for virtualization, the VMM could only use software techniques for virtualizing x86 processors and providing virtual hardware.