Hypervisors 101

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Hypervisors can be a cost efficient solution to managing multiple virtual machines on one server.

A hypervisor is in no sense a new idea when it comes to computing and virtualization. However, the widespread use of hypervisors in an enterprise IT environment is. This hardware virtualization technique allows multiple operating systems to run concurrently on the same host. In terms of efficiency, maintenance and other benefits that come with consolidation, hypervisors are where it's at. But there are also challenges when it comes to installing and switching over to a hypervisor. Here we'll break down the hypervisor basics.

What Is a Hypervisor?

Hypervisors are virtual machines that manage multiple operating systems from one piece of physical hardware. These operating systems are referred to as guests, and through the hypervisor's resources, they can be distributed in a variety of ways to meet users' computing needs. For instance, a virtual machine with 4 GB of RAM and 120 GB of hard drive space can easily and instantly be scaled up with the use of hypervisor, negating the need to buy extra hardware.

The History of the Hypervisor

Dating back to the mid-1960s, the term hypervisor has been around for more than four decades. It was created to differentiate from the term supervisor, or supervisory programs, on IBM mainframes. However, a recent resurgence in virtualization has led companies to develop hypervisors for PCs operating on the Intel x86 architecture and also on mobile phones.

Initially, hypervisors were used as a sandbox for programmers debugging and developing operating systems. The hypervisor allowed them to work without using all of the hardware’s resources. Eventually, this evolved into running multiple environments on one machine concurrently.

It was not until the 1990s that research began concerning commercial hypervisors. The major benefit to businesses was a huge savings in capital expenditures. Instead of buying multiple servers and hardware, a business could adopt a strategy where virtualization made it possible to run the same environments on less hardware. (To learn more, read Virtualization: A Move Toward Efficiency.)

Understanding the Hypervisor

While hypervisors have proved to be a beneficial step for many companies, choosing a type of hypervisor to adopt can be a tricky process. Besides the multiple vendors, there are also two types of classifications for hypervisors.


A type 1, or "bare-metal", hypervisor is a hypervisor that has no underlying operating system. This means that all of the virtual machine's (VM) resources are running through the hypervisor via paravirtualization.

Paravirtualization is a process in which a software interface is presented to a VM. This process allows the VM to operate more efficiently by reducing the time it takes to execute certain operations that would otherwise be run on a non-virtual machine. Common type 1 hypervisors include Citrix XenServer and VMware ESXi.

The other classification of hypervisor is a type 2, or hosted, hypervisor. This version of hypervisor runs on top of an underlying operating system. This means that a type 2 hypervisor relies heavily on the host operating system. If the operating system fails, so does the hypervisor. Some examples of type 2 hypervisors are VMware Server and Windows Virtual PC.

diagrams of hypervisor types - Type 1 native and Type 2 hosted

Source: Wikipedia Commons

What This Means for the Future

There is a lot of discussion revolving around what hypervisors mean for the future. Because they're the backbone of cloud computing, they have an important role for any business looking to make the jump to the cloud.

One of the largest impacts they have is on capital expenditure. Being able to virtualize hardware reduces expenses and makes scaling a company down or up much easier. This leaves an IT department with more time to focus on strategy, rather than getting bogged down with upkeep.

Companies who use virtualization may also enjoy savings on the utility bill. With less hardware, a company spends less on electricity, which can make a difference in budgeting strategies. (Virtualization is a part of green IT. Read more in 6 Reasons Why Green IT Is Pure Gold for Business.)

Overall, what this means for the future is that an IT department can focus its budget more on improving the IT environment rather than maintaining one with better and faster hardware every fiscal year.

Transitioning to a Hypervisor

The first step in transitioning to a hypervisor is deciding which type of hypervisor to run. Type 1 hypervisors are the preferred method due to their self reliance. However, both approaches yield the same results and can benefit an IT environment.

While there are many vendors to choose from when selecting hypervisors, three stand out in the market. Deciding on which one to choose depends on what you are looking to accomplish and what your environment already has.

  • VMware vSphere: Originally developed as VMware Infrastructure 4, vSphere is a type 1 hypervisor that is recognized as the market leader in server virtualization. VMware debuted in 1998, and was acquired by EMC Corporation in 2004.
  • Citrix XenServer: XenServer is a type 1 hypervisor formerly known as XenSource. Acquired by Citrix Systems in 2007, XenServer is the second most popular hypervisor on the market. Xen was originally developed as a research project at the University of Cambridge.
  • Microsoft Hyper- V: Hyper-V originally hit the market with Windows Server 2008. It can be both a type 1 and type 2 hypervisor. It offers direct integration with Windows Server systems and is proving to be a strong candidate for hypervisors.


With the widespread enthusiasm toward cloud computing, the hypervisor is the backbone to any cloud environment. Allowing near-instant scalability means greater efficiency and lower costs.


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Josh Wolanin
Josh Wolanin

Josh Wolanin is a freelance writer and IT professional based out of Minneapolis. His main areas of interest include startups, entrepreneurs, venture capital, enterprise IT, cloud computing and gadgets. He is an internationally published journalist who has been writing and working in the IT industry for more than two years.