What Is Hypervisor?

A hypervisor is a software layer installed on the physical hardware, which allows splitting the physical machine into many virtual machines. This allows multiple operating systems to be run simultaneously on the same physical hardware. The operating system installed on the virtual machine is called a guest OS, and is sometimes also called an instance. The hardware the hypervisor runs on is called the host machine. A hypervisor management console, which is also called a virtual machine manager (VMM), is computer software that enables easy management of virtual machines.

Types of hypervisor

There are two types of hypervisors: type 1 hypervisors and type 2 hypervisors.

Type 1 hypervisor is also called a native or bare-metal hypervisor that is installed directly on the hardware, which splits the hardware into several virtual machines where we can install guest operating systems. Virtual machine management software helps to manage this hypervisor, which allows guest OSes to be moved automatically between physical servers based on current resources requirements.

Benefits of type 1 hypervisors

• Fault tolerance: when the physical server fails, the management software migrates instances to available servers so quickly that we don’t even realize the physical hardware failed. Users will not experience any downtime, and the failed hardware can be repaired or replaced at a time convenient for maintenance and operations staff.
• Over/dynamic allocation of RAM capacity: when running multiple instances on a server, the total RAM allocated to the virtual machines can be larger than the total physical memory capacity of the underlying hardware.

Type 2 hypervisor is also called hosted hypervisor, which is installed within a host operating system, with the advantage that there’s no need to have a hypervisor management console. Type 2 hypervisors don’t support over/dynamic allocation of RAM, so care is required when allocating resources to virtual machines.