Managing small virtual environments (Part 4) – The Players

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In part 1 of this series, you learned about some of the basics behind virtualization and why even small organizations should consider either getting into virtualization or expanding their virtualization efforts. You also learned about how some common arguments against virtualization can be refuted.

In part 2 of this series, you learned about some virtualization myths and why they are mostly busted.

In part 3 of this series, you’ll learn about some of the high level concepts and features that are found in virtualized environment.

In this, part 4, we’ll look at the types of virtualization that are available and describe the primary players in the hardware virtualization market.

The overall market

There are a number of players both large and small in the hypervisor space these days.

  • VMware vSphere
  • Microsoft Hyper-V
  • Citrix XenServer
  • Oracle VM
  • KVM

In reality, however, only three—VMware, Microsoft and Citrix—stand out at present, although KVM is gaining in popularity, particularly among open source advocates. That said, KVM does not yet have a major presence in the enterprise, so my focus here will be on VMware and Microsoft.

Types of virtualization

Before I get into the various vendors that make up the modern virtualization market, I think it’s important that you understand that there are different kinds of virtualization out there. Although our focus in this series is on hypervisor-driven hardware virtualization, there are other types of virtualization out there that are often discussed. In order to help avoid confusion, I’ll describe those here.

Hardware virtualization

This is the type of virtualization being discussed in this series. Under hardware virtualization, an entire virtual machine is abstracted from the hardware and created in order to replicate a physical server.

Application virtualization

Whereas hardware virtualization abstracts the operating system from the hardware, application virtualization abstracts an application from the operating system. This makes it possible, for example, to run an application designed for Windows 2000 on Windows 8, even if that application does not support running on Windows 8.

Application virtualization also makes it easier to manage and deploy applications. With traditional application deployment methods, there are a number of dependencies that must be met at the operating system level and the application has to go through its formal installation routine in order to be made usable.

With an application virtualization tool, the application no longer needs to go through its installation routine. Instead, as a part of the virtualization process, the application is placed inside a sort of “wrapper.” This wrapper includes everything that the application needs in order to operate.

Session virtualization

Even if you’ve never heard the term “session virtualization,” you’ve probably used session virtualization tools before without realizing it. If you’ve used the Windows Remote Desktop tool to connect to a Windows machine, you’ve experienced session virtualization firsthand. With session virtualization tools, users no longer connect to a physical desktop; instead, users connect to a virtual manifestation of the desktop, which is created on-the-fly when the user connects to that machine.

In the Windows world, Citrix perfected the art of session virtualization with their MetaFrame product that became available in the 90s. With this product, Citrix brought to the world of IT what was an early effort to rein in the cost of desktop deployments.

Network virtualization

Virtualization is not limited to servers and applications. Network virtualization has been around for quite some time and is a way to abstract physical network ports to more easily manage the network. Now, rather than all ports on a particular network segment needing to be physically close to one another, a virtual LAN can be created that includes ports from across the organization. This abstraction allows administrators to move physical network ports between virtual networks at will without having to touch the network at all; the entire process is handled in software.

Desktop virtualization

Server’s aren’t the only hardware that can be virtualized. Today, virtual desktop infrastructure (VDI) is an increasingly popular way to deploy devices to user desktops. Now, rather than provide users with a full desktop computer, they’re provided with a thin client which is a terminal that allows them to access their own virtual machine, which houses there desktop. Desktop virtualization is really just a form of hardware virtualization.

Hypervisor types

In the world of hardware virtualization, there are basically two types of hypervisors in use.

The Type 1 hypervisor is the one that we’re focused on in this series. Also referred to as a bare metal hypervisor, the type 1 hypervisor installs directly onto the server hardware. The hypervisor then controls access to the server hardware and schedules resource time among the virtual machines that are requesting access to resources.

A Type 2 hypervisor installs on top of an existing operating system. As such, it’s not nearly as efficient as a Type 1 hypervisor, but these kinds of tools can be extremely useful in development, test and lab environments. A type 2 hypervisor, when installed to Windows, for example, simply runs just like any other application.

The current hypervisor players

As mentioned previously, the primary players in today’s datacenter virtualization market are VMware, Microsoft and Citrix.

VMware reinvents virtualization

Although virtualization may seem to be a new and revolutionary technology, the fact is that it’s been around for a very long time. Virtualization was used as far back as the early 1960s as a way to improve mainframe hardware utilization.

VMware is sometimes credited with creating virtualization. What the company actually did was bring this technology to the x86 server market. What VMware can be credited with is ushering in a new era of computing in the generalized server space and in re-inventing the data center.

VMware’s first version of their ESX product was released in 2001. Today, the company’s ESXi—a more nimble version of the original ESX—ships with the company’s latest release of their product, dubbed vSphere 5.1.

VMware is still considered the gold standard when it comes to virtualization.

VMware sells a number of different hypervisor products. ESXi/vSphere happens to be the one that supports millions of enterprise level workloads and is a type 1 bare metal hypervisor. However, the company also sells type 2 hypervisors for both Windows and Macintosh.

VMware Workstation is a type 2 hypervisor that runs under Windows. VMware Fusion is the Macintosh equivalent.


Although late to the game, Microsoft has spent the past few years with a hypervisor that some considered “good enough” when compared to vSphere. That said, Microsoft’s Hyper-V 2008 R2 hypervisor was a far, far cry from the vSphere product, with far fewer features and far less overall polish and functionality than vSphere. This is another reason that vSphere remains the market leader.

Like ESX, Hyper-V is a type 1 hypervisor, although it’s often thought of as a type 2 hypervisor due to the way that the tool is installed. Once Windows Server is deployed, Hyper-V is installed as a role. However, when this takes place, Hyper-V is installed into the kernel, which sits directly atop the hardware and the Windows instance becomes a “parent partition.” Although Hyper-V is dependent on that parent partition, it’s still considered a a type 1 hypervisor.

In late 2012, Microsoft released version 3 of Hyper-V, dubbed Hyper-V 2012. With this release, Microsoft has leapt forward with their hypervisor technology. In some ways, Microsoft remains a bit behind VMware, but in others, the company has absolutely caught up with VMware in terms of features. In terms of ease of use, I still believe that vSphere is a bit easier to manage, but when you consider Hyper-V’s price tag—free—a significant decision about the meaning of “ease of use” needs to occur. After all, a free hypervisor with complete enterprise-grade features is certainly compelling.

In Windows 8, Microsoft has also shipped a client version of Hyper-V 2012.


In 2007, Citrix entered the hardware virtualization market with the company’s acquisition of XenSource, the developer of virtualization management tools for the open source Xen hypervisor. The result: Citrix XenServer, a commercially supported hypervisor which also enjoys support from the open source community.

There are a number of other hypervisor vendors that use the open source Xen hypervisor as their product foundation:

  • Citrix XenServer
  • Oracle VM
  • Virtual Iron

XenServer is also a Type 1 bare metal hypervisor.


In this article, you learned about the major players in the virtualization market. In the next part of this series, we’ll go over the features and licensing terms for each product.

If you would like to be notified of when Janique Carbone releases the next part in this article series please sign up to our Real-Time Article Update newsletter.

If you would like to read the other parts in this article series please go to:

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