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VMware has been working hard for the past ten years to develop the x86 virtualization market, and the company has done a good job of it. Today, VMware's virtualization portfolio includes ten different virtualization tools and a plethora of management utilities that tackle anything -- from resource load balancing to workflow automation for virtual machine (VM) requests. This effort has granted them a well-deserved 80% of the current marketplace for server virtualization.
Now, with the release of the Hyper-V role for Windows Server 2008, Microsoft obviously wants its own share of the market. This is the first time Microsoft has had a hardware-based virtual machine engine. Previously, the company had released two software-based virtualization products -- Virtual PC and Virtual Server. Both were derived from the technology Microsoft acquired from Connectix Corp., the original makers of Virtual PC. Connectix first made its name when it began producing software that allowed Macintosh users to run Windows software on their PCs by emulating Windows on top of the Mac OS.
Software virtualization tools require an underlying operating system to run. In the cases of Virtual PC and Virtual Server, the underlying OS is Windows XP, Vista, Windows Server 2003 or 2008. In the case of VMware's software virtualization offerings, the underlying OS can be several different versions of Windows, Linux or even the Macintosh OS.
Hardware virtualization products, commonly called hypervisors, run directly on the hardware and do not require an operating system. In the case of VMware's ESXi hypervisor, this is pretty clear since the hypervisor is only 32 MB in size and is installed directly on the hardware or, even better, integrated to the server you purchase from the likes of Dell, HP, Fujitsu and others.
Operating system requirements are less clear with Microsoft's Hyper-V, since Hyper-V is a role within Windows Server 2008 and therefore requires an installation of the OS before you can enable it. However, much of the Hyper-V code is similar to that of Citrix XenServer -- which is also a hardware virtualization tool -- only this time it's built upon the Xen extensions to Linux. It's important to note that XenServer also requires some Linux code to run.
Unlike VMware's similar offerings, the two Microsoft software virtualization tools will only run x86 or 32-bit virtual machines. In the case of VMware, all of its virtualization products, both hardware and software, will run x86 and x64 virtual machines so long as you install them on a machine using an x64 processor. Microsoft's Hyper-V, however, will only install on an x64 machine and will support select x86 and x64 VMs (see Table 1).
Table 1: VMware versus Microsoft Hypervisor Guest OS Support
| Metric |
VMware |
Microsoft |
| Guest OS Support |
Microsoft Windows
3.1/3.11/95/98/Me/NT/2000/
2003/2008/XP/Vista x86 or
x64
MS-DOS 6.x
Red Hat Enterprise Linux
2.1/3/4/5
Red Hat Advanced Server 2.1
Red Hat Linux 7.2/7.3/8.0/9.0
SUSE Linux Enterprise Server
8/9/10
SUSE Linux 8.2/9.0/9.1/9.2/9.3
FreeBSD 4.9/4.10/4.11/5.0
TurboLinux 7.0, Enterprise
Server/Workstation 8
Novell Linux Desktop 9
Sun Java Desktop System 2
NetWare 6.5/6.0/5.1
Solaris 9/10 for x86
|
Microsoft Windows
2000/2003/2008/XP
Pro/Vista x86 and x64
SUSE Enterprise Linux
Server 10 SP1 |
| 64-bit Guest Support |
Most x64 OSes |
Windows 64-bit OSes |
Note that Table 1 outlines the guest operating systems that are supported by both vendors on their hypervisors. While Microsoft does not support products like Windows NT on Hyper-V, this does not mean you cannot run the OS inside a virtual machine on this hypervisor. It only means that if you do, Microsoft will not support the operation on Hyper-V. There is no loss there since Microsoft stopped support for Windows NT in 2004.
A virtual machine is a virtual machine, and if you can build it, chances are very good it will run on top of pretty much any hypervisor that recognizes the format of the virtual disks that make up the machine. Performance may not be great, but running a machine as a VM is so much better than running a machine on a physical box that you may be better off anyway.
Microsoft's Hyper-V is a version 1 product and, as many have already pointed out, it lacks several features available in other hypervisors. However, the very fact that it is built on and included in Windows Server 2008 will likely make it a popular choice. It won't be because of the price, however, because at $28 per box, Hyper-V is still more expensive than the free VMware ESXi installable edition. No, it will be popular because people are familiar with Windows Server and will want to take advantage of its complete features set.
Hyper-V can be installed on either the full installation or the Server Core installation of Windows Server 2008. Most small organizations will probably run it on the full installation since that's what they are familiar with, but we would recommend they use Server Core.
Server Core is a minimalist installation of Windows that was designed with Hyper-V in mind. It does not include Internet Explorer, Windows Contacts or Windows Media Player components, and because of this, it does not require updates as frequently as the full installation. In addition, because it is a minimalist version of Windows Server 2008, it doesn't require as much overhead as the full installation, which frees up more resources for the virtual machines you would run on top of it.
Will Hyper-V have an impact? There is no doubt that it will. Will it displace VMware ESXi? Only time will tell. Right now, Hyper-V is in its infancy and needs to mature significantly before it can play the same role in the data center that VMware does today.
Can Microsoft really make an impact with Hyper-V?
Danielle Ruest and Nelson Ruest are IT professionals specializing in systems administration, migration planning, software management and architecture design. Danielle is Microsoft MVP in Virtualization and Nelson is Microsoft MVP in Windows Server. They are authors of multiple books, including the free 
