Achieving Enterprise Xen

By Marcia Gulesian

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The buzz, which turned out to be a roar, at LinuxWorld Boston 2006 was virtualization. And, the product which captured the lion’s share of attention in this arena was Xen 3.0 from XenSource, a free open source virtualization operating system that acts as a small, low-level hypervisor—a fancy word for a scheme which allows multiple operating systems to run, unmodified, on a host computer at the same time.

Making a powerful case for using Xen was CTO Kevin Kettler from Dell. In his keynote, he demonstrated a Dell PC running Red Hat Enterprise Linux in one virtual machine and Windows Server 2003 in another.

Each operating system could access Web pages hosted by the other, communicating through the Xen hypervisor, which manages virtualization. Xen is the industry's only hypervisor today that supports Virtualization Technology (VT). With Intel's VT and Advanced Micro Devices' AMD-V, the same system can run Windows or Linux.

Kettler expounded that virtualization is making significant headway in the enterprise and that Dell was investing significantly in virtual machine technology born out by Dell’s use of Linux in its own supercomputers.


Xen 3.0 has a compelling feature set that is targeted at enterprise- level virtualization needs. Xen supports symmetric multi-processing (with an ability to dynamically hot plug CPUs to ensure the best use of available resources), the addition of large server memory configurations and near-native performance, and offering for the first time an ability to virtualize all guest operating systems.

Originally developed for x86 machines, support for the IA-64 (Itanium) and Power5 (Mac) platforms is currently underway. Xen has already gained wide acceptance in the Linux server market in 2005. Linux and versions of Unix were the first operating systems ported to Xen, specifically Linux 2.4, 2.6, but any Linux distribution (RedHat, SuSE, Debian, Mandrake) should run unmodified over the ported OS.

A port of Windows XP was developed for an earlier version of Xen, but is not available for release due to license restrictions. However, Xen 3.0 has included support for Intel’s VT-X Vanderpool architecture extensions. This technology will enable unmodified guest operating systems to run within Xen virtual machines, if the host system supports the Vanderpool or the Pacifica extensions (Intel's, and AMD's, respectively, extensions to natively support virtualization).

In practice, this will mean that there will be a performance boost, and that it will be possible to virtualize Windows without having to modify it in any way, which licensing restrictions prevent.

Microsoft, not wanting to be left behind in this growing market, announced its support for Linux virtual machines running on its Virtual Server 2005 R2 (a free download) with free virtual machine additions for Red Hat Linux and Novell SUSE Linux and 24 x 7 technical support.

Also noteworthy, another virtualization vendor Virtual Iron announced the first fully supported commercial application on Xen. Virtual Iron v3 will use the Xen hypervisor to provide advanced virtualization and policy-based management capabilities to Xen. This release will allow users to run existing 32 and 64 bit Linux and Windows operating systems without modification.

And with a nod to open standards-based solutions, VMware, the global leader in virtual infrastructure software, announced that its virtual machine disk format specification for defining and formatting virtual machine environments is now openly available, downloadable and free of charge.

This will enable its use by all developers and software vendors and includes open licensing compatible with those operating under open source licenses, such as the GPL.

The key to the marriage between Linux and Xen is not only the wealth of virtualization offerings, but that you have cost benefits from virtualization of enterprise servers: capital expenditures and personnel costs associated with deployment and management of IT infrastructure are reduced.

Xen has the ability to instantly deploy a virtual server image on any server which dramatically cuts provisioning time from weeks to seconds. Furthermore, its live relocation capability enables no-downtime maintenance, high-availability and optimal matching of workload to available compute resources, and, as mentioned above, you can obtain the Xen/Linux software free of charge.

With all this hype around virtualization and open source Xen you might be asking yourself: Is Xen ready for the enterprise?

The consensus from industry analysts at the show agreed that Xen has reached critical mass in the developer community but has yet to see wide-spread acceptance at the Enterprise level. But, I think it is safe to say that major support and participation for Xen by IBM, Intel, Dell, Novell, and others will help drive the adoption of Xen in the Enterprise.

Marcia Gulesian has served as software developer, project manager, CTO, and CIO over an eighteen-year career. She is author of more than 100 feature articles on IT, its economics, and its management.