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 5 – VMware 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.