Understanding Hypervisors

The Virtual Machine Manager (VMM), also known as Hypervisor, is the software application responsible for running multiple VMs on a single system. It is also responsible for creation, preservation, division, system access, and VM management running on the Hypervisor layer.

The various types of Hypervisors are listed as follows:

• VMM Type 2

• VMM Hybrid

• VMM Type 1

VMM Type 2

This type runs Hypervisor on top of the OS. We have the hardware at the bottom, the OS, and then the Hypervisor running on top, as shown in the following diagram:

Microsoft Virtual PC and VMware Workstation are examples of software that use VMM Type 2.

VMs pass hardware requests to the Hypervisor, from there to the host OS and it then finally reaches the hardware. This leads to performance and management limitation imposed by the host OS.

Type 2 is common for test environments—VMs with hardware restrictions—to run on software applications that are installed in the host OS.

VMM Hybrid

When we are using the VMM Hybrid type, the Hypervisor runs on the same level as the OS, as shown in the following diagram. As both Hypervisor and the OS have the same access to the hardware and with the same priority, it is not as fast and safe as it could be. This is the type used by the Hyper-V predecessor named Microsoft Virtual Server 2005:

VMM Type 1

VMM Type 1 is a type that has the Hypervisor running in a tiny software layer between the hardware and the partitions and managing and orchestrating the hardware access. The host OS, known as Parent Partition, run on the same level as the Child Partition, known as VMs, as shown in the next diagram. Due to the privileged access that the Hypervisor has to the hardware, it provides more security, performance, and control over the partitions. This type has been used by Hyper-V since its first release: