March 15, 2019

What Is a Hypervisor?

By Tobias Geisler Mesevage

Hypervisor Definition

A hypervisor is software with only one purpose – abstracting and isolating operating systems from hardware. This abstraction allows you to host and operate multiple operating systems inside virtual machines on one physical host machine. Operating systems inside guest virtual machines share all of the host machine’s resources like processor, memory, network cards, etc.

Hypervisor Types

Virtualizing your operations saves time and money by enabling servers to do more than one thing concurrently, and do so efficiently. When you are ready to virtualize, you will need to choose between two types of hypervisors, or virtual machine monitors (VMM).

Your hypervisor will manage and provision the resources of the system. This can be achieved two ways — with two types of hypervisors:

Type 1: “Bare metal” hypervisors, which are directly installed on a server’s hardware and support hardware virtualization

Type 2: “Hosted” hypervisors, which run as applications on a server’s preexisting operating system and support software virtualization

Hypervisor Types

Bare-metal vs Hosted

Bare-metal hypervisors run without a host operating system. In fact, a Type 1 bare metal hypervisor acts as the operating system of the server. It has direct access to underlying hardware. Without a host operating system and other applications fighting for physical resources, hypervisors can use all available processing power and memory space and provision it to the guest virtual machines.

That makes bare-metal hypervisors more efficient and more effective than hosted hypervisors. Bare-metal hypervisors are the first choice for enterprise virtualization that requires the ability to optimize production and avoid technical issues.

Bare-metal hypervisors are also more secure. The lack of host operating system makes the attack surface smaller, thereby eliminating all security flaws and vulnerabilities that come with the use of operating systems. This way, each guest virtual machine is logically isolated against malicious actors.

Hosted hypervisors are usually used for development and testing when performance and security are not a concern. They are easier to install and run inside the operating system, allowing developers or system administrators to create test environments on the machine while still being able to use other applications.

The Bottom Line

Hypervisors enable virtualization and allow you to run multiple virtual machines on one physical machine. Converting physical machines to virtual ones reduces the number of needed physical machines. Applications that were earlier installed side-by-side on one physical machine are now installed independently inside virtual machines running on the same physical machine. Bare-metal hypervisors, although more complex to set up than hosted hypervisors, provide maximum performance, scalability, and stability to hosted virtual machines.

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