Virtualization: Xen vs. Microsoft vs. VMware: Page 2

Posted February 13, 2007

David Strom

David Strom

(Page 2 of 2)

Before you choose your VM server vendor, here are some questions to ask to qualify the kind of product that will serve your needs best:

1) What host hardware and operating system will you want to run?

Each VM server product hosts its virtual machines in different ways. Some, such as the free VMware Server and Microsoft's Virtual Server, run on top of ordinary Windows Server machines. There is a difference, however: Microsoft requires a lot more than just the OS to run its virtual server product. you have to run the latest SPs and IIS and Active Directory and use IE. VMware needs just the basic OS. (More on that in a moment.)

VMware Server also runs on numerous Linux distributions, and Microsoft's supports testing but not production use on XP Professional. Others, such as the paid VMware versions and Xensource, run on the "bare metal" of a PC – meaning that no OS is needed, and they install their own miniature OS to operate the various VMs. These usually support the more recently higher-performance CPUs, but finding the right drivers to run these bare metal OSes may be an issue. It depends on what host OS you’re comfortable using in your enterprise and under what conditions.

2) What guest OSes do you plan on using?

Each VM product can run just about any "guest" OS but some are better tuned and pre-configured for particular OSes. VMware has the widest support for many different Windows, Linux, and Unix OSes. Microsoft is of course more focused on their own Windows versions, and Xen supports some Windows and Linux versions and is adding more.

3) How many VM hosts do you plan on operating and how will you manage them?

Each virtual server solution has slightly different management tools and consoles to connect with the VMs that it is running. Microsoft is the most closely tied to Windows and its own software such as Internet Information Server. The management tool runs under IE v6 or later and you can view the console of each VM inside the browser frame. They have another tool that is in beta (expected in the latter part of 2007) called System Center VM manager that will require Active Directory running on the host Windows Server 2003 machine. Xensource's Administrator Console runs on both Linux and Windows.

4) How familiar are you with VM concepts and how important is support?

Part of operating VMs is having a solid base of support behind the products. VMware has been around the longest and has the best-developed reseller and support channel. While Xensource is open source, the community is still pretty new and getting started. If you have subscriptions to the various Microsoft TechNet and MSDN offerings you will have the resources to make use of its product.

5) What is the difference between free and paid products?

Each of the three major vendors offers free products: VMware Server, Microsoft's Virtual Server, and XenExpress. VMware offers three different paid versions of its Infrastructure line – Starter, Standard, and Enterprise, with corresponding price increases. All three include the basic ESX software that runs the VMs, along with management tools. The more expensive versions include support for server clustering and other high-availability options.

Xensource has two paid versions, XenServer and XenEnterprise. The former is licensed at $99 per year while the latter can be either licensed at $488 per year or purchased for a single fee of $750, so obviously for longer periods the purchase is the most cost-effective. The table below summarizes the various options for these three vendors.

Table: Virtual Server product comparison





URL server

Free server product

VMware Server

Virtual Server 2005 R2


Paid server products

Infrstructure v3 (Starter, Standard, and Enterprise)


XenServer and Enterprise

Pricing range paid product

$1000 - $5750 (two CPU versions)


Server : $99/yr Enterprise: $750

Host OS (if any)

Server:Windows Server 2003, various Linux

Infra v3:bare metal

Windows Server 2003 SP1, XP Pro SP2 (for testing purposes only)

Bare metal

Management tools

Virtual Center

VMotion migration tool

System Center VM Manager (beta)

Administrator Console

Support resources





  • Widest selection of pre-built appliances
  • Widest selection of guest OS support
  • Wizards galore for install aids
  • Can run on any IE browser with Internet access
  • Less expensive option
  • Easy cloning of VM images

Open source solution that doesn't require any host OS


Confusing array of pricing and configuration options

Only four "virtual hard disk" pre-built appliances of MS server products

  • Limited hardware support
  • Limited Windows guest OS support

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