Open Source virtual server software a likely dark horse

When hardware from Intel and AMD arrives next year, Windows shops will have a price friendly option for server virtualization that comes from the open source community.

When new hardware that supports virtualization technology comes on the market next year, IT managers will have more to choose from than popular software from VMware Inc. and Microsoft.

Windows shops will likely be looking over the Xen 3.0 hypervisor and commercial products built on this release, such as software from XenSource Inc., in Palo Alto, Calif. Xen is an open source alternative for x86 computers that can execute multiple virtual machines, each with its own operating system (OS), on a physical system. The latest release, Xen 3.0, is expected out in early November.

"I plan to download it and install it and run some applications on it in testing mode," said Jamey Vester, an administrator at Subaru of Indiana, Lafayette, Ind., who runs a Windows shop and uses VMware's ESX software.

Virtualization software gains interest

Server virtualization software lets administrators place multiple virtual servers on a single physical device. By doing this, IT administrators can consolidate their servers and therefore get more for their hardware investments.

It's an emerging technology being watched with great interest by administrators and IT executives alike. In a poll of 603 infrastructure decision makers taken by Forrester Research Inc., in Cambridge, Mass., in early 2004, only 22% were aware of or interested in this technology.

By the middle of 2005, 29% of IT executives polled said they were interested in using virtualization and another 29% were interested in testing or using the technology within the next year. About 61% planned to increase the scope of their installations, the report said.

And the number of Windows shops interested in virtualization may multiply faster now that Microsoft has changed the way it licenses virtual machines. In December, customers running premium versions of Windows will no longer have to pay per physical server.

The competition is fierce

Today, for virtualization that needs to be done on the x86 platform, the choice is between VMware software and Microsoft Virtual Server 2005, said Richard Fichera, a Forrester analyst.

But the combination of Xen 3.0-based technology coupled with the release of Advanced Micro Devices Inc.'s Pacifica and Intel Corp.'s VT hardware will make it possible for Xen to vitualize Windows in a high-performing and efficient manner. Xen already supports Linux.

The next release of Xen also includes support for symmetric multiprocessing and up to 32 virtual processors. It also supports both 32-bit and 64-bit addressing and has a live relocation feature, which means an administrator can move a running virtual machine from one PC to another.

Other Xen 3.0 features include support for physical address extension, better copy-on-write file system support, better cluster transparency and some improvements to its quality of service features, such as real-time scheduling capability. There is also a set of debugging tools.

Making virtualization work

When there are multiple OSes virtualized on a server, each one thinks it is in control of the whole machine. But the virtualization software can cut the performance of the server if the virtualized OS attempts to do tasks as if it really were the only OS on the machine, such as put pixels on display or write to the disk. There is a performance drain created from the overhead that occurs when virtualization software has to patch the OS on the fly.

To avoid this problem today, Xen uses para-virtual device drivers. They allow the guest OS to be "aware" it is being virtualized, said Simon Crosby, vice president of strategy and corporate development at XenSource.

The x86 conundrum

It is the nature of an x86 device to be hard to virtualize because of the way that the system assigns privilege. To run an unmodified operating system in an efficient manner, as you would want to run Windows, requires the use of VT and Pacifica, Crosby explained.

Once the hardware support from Intel and AMD is in place, Xen and Windows will then be able to run unmodified, thereby receiving this needed performance boost.

For Windows customers to get similar virtualization features from Microsoft, they have to wait a few years. The software vendor said it would offer a hypervisor for the R2 release of Longhorn Server, which itself isn't due until sometime in 2007.

Microsoft is aiming its products at VMware's ESX and GSX products. GSX compares most closely with Virtual Server, as it runs on top of a host operating system. VMware's ESX is a hypervisor that runs directly on server hardware and therefore performs faster. VMware also offers VMotion, which lets users move a live server from one virtual machine host to another without interrupting the service.

Virtualization can be pricey

If customers want VMware, they can expect to pay more. Virtual Server 2005 is $999 for up to 32 processors. GSX sells for $2,800 for up to 32 CPUs. And ESX sells for $3,750 for a two-CPU server. But pricing aside, VMware has a seven-year market advantage and a good reputation with enterprise customers.

"VMware isn't very expensive compared to a few minutes of downtime on my server," Subaru's Vester said.

VMware recently made its source code accessible to its partners with the hope of developing more collaborative relationships with them. The relationship may also lead to the exploitation of the properties of virtualization in other network elements, such as switches or network cards.

XenSource hasn't revealed its product line yet but the company is expected to offer Xen technology with management features.

The Microsoft question

Once Microsoft builds virtualization technology into its OS, it remains to be seen whether customers will feel they need other products. XenSource's Crosby said it depends on whether an IT shop wants to reap the benefits of virtualization now or later. There is a window of time to take advantage of an inexpensive way to do this. Xen, after all, is free, he said.

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