Hypervisor 101: Understanding the Virtualization Market

Over the past decade, virtualization technologies have gone from small shop and educational tools to full blown IT solutions. In the past, many major software vendors would explicitly say that their software will not work in a virtual state and will not be supported if the end-user decided to virtualize. Now, the technology has changed and evolved. Matching the needs of the industry to create a more efficient infrastructure – virtualization was re-born as a powerful platform.

Some of the biggest software makers are now creating design and best practices around a virtual infrastructure. The industry has shifted from 1-to-1 hardware platforms and has created a more efficient data center in which resources are shared between numerous workloads. Starting with VMware, there were many other secondary players in the market place during the early days. As acquisitions and attrition have taken their toll, the top three vendors in the hypervisor space have emerged. Prior to taking a look at those competitors, it’s important to have a clear understanding  of what a hypervisor really is and what it does.

The modern hypervisor: A high-level explanation

The evolution of virtualization greatly revolves around one piece of very important software. This is the hypervisor. As an integral component, this software piece allows for physical devices to share their resources amongst virtual machines running as guests on to top of that physical hardware. To further clarify the technology, it’s important to analyze a few key definitions:

  • Type I Hypervisor. This type of hypervisor (pictured at the beginning of the article) is deployed as a bare-metal installation. This means that the first thing to be installed on a server as the operating system will be the hypervisor. The benefit of this software is that the hypervisor will communicate directly with the underlying physical server hardware. Those resources are then paravirtualized and delivered to the running VMs. This is the preferred method for many production systems.
  • Type II Hypervisor. This model (shown below) is also known as a hosted hypervisor. The software is not installed onto the bare-metal, but instead is loaded on top of an already live operating system. For example, a server running Windows Server 2008R2 can have VMware Workstation 8 installed on top of that OS. Although there is an extra hop for the resources to take when they pass through to the VM – the latency is minimal and with today’s modern software enhancements, the hypervisor can still perform optimally.
  • Guest Machine. A guest machine, also known as a virtual machine (VM) is the workload installed on top of the hypervisor. This can be a virtual appliance, operating system or other type of virtualization-ready workload. This guest machine will, for all intents and purposes, believe that it is its own unit with its own dedicated resources. So, instead of using a physical server for just one purpose, virtualization allows for multiple VMs to run on top of that physical host. All of this happens while resources are intelligently shared between other VMs.
  • Host Machine.  This is known as the physical host. Within virtualization, there may be several components – SAN, LAN, wiring, and so on. In this case, we are focusing on the resources located on the physical server. The resource can include RAM and CPU. These are then divided between VMs and distributed as the administrator sees fit. So, a machine needing more RAM (a domain controller) would receive that allocation, while a less important VM (a licensing server for example) would have fewer resources. With today’s hypervisor technologies, many of these resources can be dynamically allocated.
  • Paravirtualization Tools. After the guest VM is installed on top of the hypervisor, there usually is a set of tools which are installed into the guest VM. These tools provide a set of operations and drivers for the guest VM to run more optimally. For example, although natively installed drivers for a NIC will work, paravirtualized NIC drivers will communicate with the underlying physical layer much more efficiently. Furthermore, advanced networking configurations become a reality when paravirtualized NIC drivers are deployed.

Now that there is a better understanding of the hypervisor and the various components which fall under it, we can examine the major players in the industry.

The “Big Three” Hypervisor Vendors

Although there are several smaller organizations which are developing their own hypervisor technologies, three manufacturers have really taken the market by storm with their solutions. As leaders in the space, there are specific differentiators between the products. This doesn’t mean one is necessarily better than the other;  rather, it means that there may be a better fit for one hypervisor over another.

VMware vSphere 5VMware has come a long way in the hypervisor market. It still commands the top spot within the server virtualization world and makes some of the best application and desktop virtualization technologies. As VMware continues to evolve, the product is known for its feature-rich suite capable of some very powerful solutions. Integration with DR, SAN, LAN and WAN technologies makes VMware an intricate component to many modern data center environments. One of the biggest challenges facing a potential customer is understanding which feature and license set is required for a given project. Prior to any purchase, the IT team should plan out the deployment and have a clear picture to which features are key for the environment.

Citrix XenServer 6 – As a leader in the application virtualization and delivery markets, it was only a matter of time before a hypervisor came into the picture. Originally known as XenSource, XenServer was born from an open source world and built upon enterprise technologies. Development of the XenServer platform has come a long way. Now, more organizations are deploying this technology into their production and test systems which are capable of handling a global load. The entry price point for the hypervisor is very enticing and the Enterprise version contains many of the necessary enterprise features which administrators demand. Failover, HA, shared resources and other key components are all native to the hypervisor and are ready for production rollouts. Arguably second in the server virtualization space, XenServer continues to innovate and expand its product offering.

Microsoft Hyper-V 3 – With the latest release of Windows Server just around the corner, there has been a lot of excited conversation revolving around the latest iteration of Microsoft’s Hyper-V. Already a solid platform, some limitations are being directly addressed with the new released. Live migration, storage resource pools and even cloud backup capabilities are all being built into the new hypervisor technology. Couple that with the very low price point to purchase – and we may very well see a new powerhouse emerging. The newest version of Hyper-V looks to take some serious market-share away from both Citrix and VMware as it deploys a more production and enterprise ready hypervisor. The direct integration with Windows Server systems will make this product even more enticing.

Although VMware is currently the market leader within the virtualization space, others are quickly emerging as leaders in their space. Remember, in this article, we’ve mainly been discussing server virtualization. As industry demands have grown, technologies have expanded beyond the server. Now, there are technologies for application virtualization (ThinApp and XenApp) as well as technologies which can virtualize desktops (XenDesktop and View). The entire idea behind a virtual data center is to create a more efficient environment which is easier to manage and orchestrate. Furthermore, concepts such as DR and physical server consolidation are all made easier when virtualization is introduced. There is very little doubt that the technology will continue to be adopted and improved. The exciting part is watching how further innovations can help organizations of all sizes align their business goals with their IT infrastructure.

Bill Kleyman is a Virtualization and Cloud Architect, MTM Technologies, who enjoys writing about technology and cloud.

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About the Author

Bill Kleyman is a veteran, enthusiastic technologist with experience in data center design, management and deployment. His architecture work includes virtualization and cloud deployments as well as business network design and implementation. Currently, Bill works as the Vice President of Strategy and Innovation at MTM Technologies, a Stamford, CT based consulting firm.

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  1. Hi Bill; Thanks for the article. You had mentioned other virtualization environment besides server virtualization. I was hoping you talk about storage virtualization as well. I've found some great products at stonefly.com.

  2. Incomplete article . No mention of IBM technologies , Power VM and also the fact that virtualization was invented by IBM .

  3. @balaraju Great observation! However, I wouldn't say that makes an article incomplete :) Certainly, the goal wasn't to go into an in-depth discussion of the history of virtualization. Which, on that note, you are correct - was created by the smart folks at IBM. Rather, this article was designed to take a look at the hypervisor market from today's perspective. Although a solid platform, PowerVM isn't a massively adopted virtualization platform. Perfect for UNIX, Linux and IBM i clients, it's still fairly safe to say that VMware holds the reigns on the server virtualization front. Thanks for the feedback!

  4. Missing info on Red Hat's virtualization offerings. Red Hat has been growing and its virtualization has caught on. Missing information on whether Microsoft Hyper-V will run anything but Windows. Knowing the company's long history Microsoft's solution is only for Microsoft-only IT shops.

  5. you comment posters don't get it. not sure why you bother posting. He isn't talking about every clown who has a hypervisor offering, he is talking about the top 3 current ones that are worth considering, not the top 4 or 10... \ you are probably trying to say KVM, which was not red hats from conception. they wanted to jump on the vm train so they 'bought' KVM a few years ago. talk about missing information... 8)

  6. hitechken

    Greg, great comment! He is talking about TOP 3, man can people get their panties in a bunch quickly! Interesting comment from Ze'ev about MS, we are only using Citrix and VMware in our DC, but not sure if MS is 'open' to other software and if it plays nice in the sandbox!

  7. Andrea

    Altough some Unix hypervisors (IBM, HP and SUN) are still there but nearly dead (they have a niche in the market). My opinion is htat Citrix Xenserver is losing market for KVM and Xen virtualization on linux systems and Openstack cloud stack.

  8. When it comes to bare metal server vs virtualization, and it’s important to understand the benefits and applications of each option. With visualization the bare metal server (the physical server) is split up into multiple virtual servers. This type of technology is best suited to horizontal scalability such as a website with high traffic volumes or cloud software.