When it comes to computing, think of virtualization like the high occupancy vehicle (HOV) lane of a major highway.

Virtualization is essentially the shared usage of computer resources among a large group of users. Like carpooling, in which commuters share in the cost of fuel, the goal of virtualization is to increase the efficiency of both the end users and the expensive computer resources they share.

“Where you goin’ fool!? Me too, hop in!!!”

Traditional servers (computers that literally serve files, data, and applications to other computers) consisted of a single, physical combination of processing, storage, and networking resources.

They ran one operating system, and most operated at just 5 to 15 percent of their total load capacity.

Virtualization enabled multiple operating systems to run on a single server.

Modern server resources tend to be very robust (think dozens of computer chips, trillions of bytes of memory and storage, and high-speed network connections). All of these resources are aggregated, pooled, and allocated to virtual machines, which are software versions of computers.

End users (me and you, yo mama and yo cousin too) connect to the files, folders, websites, and other programs installed on these virtual machines as if they were installed on physical machines.

The Main Ingredient: the HYPERVISOR (aka the Virtual Machine Monitor)

Virtualization's essential component is known as the hypervisor.

The smart people at IBM, who invented virtualization, called the hypervisor the virtual machine monitor (VMM for short).

The hypervisor (depicted below as the virtualization layer) is software installed on a computer or server that allows it to share its resources.

Hypervisors are classified as one of these two types:

Classification	Characteristics and Description
*Type 1: bare metal* or native	Bare metal (native) hypervisors are software systems that run directly on the host's hardware to control the hardware, and to monitor the guest operating systems. Consequently, the guest operating system runs on a separate level above the hypervisor.
*Type 2: hosted*	Hosted hypervisors are designed to run within a traditional operating system. In other words, a hosted hypervisor adds a distinct software layer on top of the host operating system, and the guest operating system becomes a third software level above the hardware.

Source: Oracle

The major virtualization products (and vendors) you will encounter today are:

VMware and the vSphere hypervisor

Microsoft, which produces Hyper-V and Azure

Citrix and the Xen hypervisor

Red Hat, a Linux distribution that utilizes a hypervisor called KVM.

…and Amazon Web Services

I have administered and engineered some combination of these different technology solutions for over 10 years. I am certified on the VMware, Microsoft, and Citrix platforms. I have previously written about the importance of certifications, and particularly starting your career with CompTIA A+. According to the latest A+ exam objectives, here’s what you need to know about virtualization:

The focus appears to be on the Type 2, hosted hypervisor, so review the following:

Client-Side Virtualization

As you build knowledge and progress in your career, other relevant virtualization technologies will become more relevant (and prevalent). I encourage you to get familiar with them. They include:

Hybrid cloud

Containers

~and~

Hyper-convergence