XenSource Shifts Gears as It Rolls Out XenEnterprise Virtualization

Published: April 4, 2006

by Timothy Prickett Morgan

It was only a year ago when the open source Xen hypervisor project took LinuxWorld by storm and suddenly became one of the most important open source projects ever launched and a key piece of the Linux software stack. At the time, the company behind the project, XenSource, had been more or less quickly created and backed with venture funding and had made plans to have commercialized products that rode atop the Xen hypervisor to market in early 2006.

Well, here it is, early 2006 and another LinuxWorld is in full swing in Boston, and XenSource has a new management team in place that has decided that it is better to partner with the major IT players and focus its efforts on creating products that server makers and operating system suppliers can weave into the products. The alternative, which this new management team rejected, was to create software and services that XenSource itself would sell. It is a lot easier to get access to those massive sales and reseller channels of the big IT players if you position yourself as a partner, and that is the picture that XenSource was painting yesterday as it rolled out its first commercial products based on the Xen hypervisor it created.

While Ian Pratt, the senior faculty member at Cambridge University, is still the leader of the Xen project and its chief architect and Simon Crosby, who was also a faculty member at Cambridge as well as a researcher at Intel, is still chief technology officer at XenSource, the company has some pretty serious managers now. In February, XenSource tapped Peter Levine, a former executive vice president at Veritas who ran about a third of that company's business before it was acquired by Symantec, as its president and chief executive officer. John Bara, who ran the financing operations around the Intel Pentium processor, is now vice president of marketing at XenSource, and Frank Artale, who was the CEO at Consera Software before Hewlett-Packard acquired it and was also vice president of Windows solutions at Veritas and general manager of the Windows 2000 group at Microsoft, is now vice president of business development. This new team has decided it is better to become the de facto standard hypervisor for the workstation and server industry and to make money by being a good partner with the platform providers.

That's why you won't hear anyone at XenSource talk about how they are going to run VMware out of business as the company unveils how it will package the Xen 3.0 hypervisor, which began shipping in December and which has already seen more than 60,000 downloads since that time. What XenSource is focusing on is a "massive hardening effort," says Crosby, that it is undertaking with the server and operating system vendors, which seeks to get the latest Xen 3.0.2 implementation ready to support the virtualization features in future Intel and AMD 64-bit processors, which provide hardware-assisted processor instruction set virtualization through their respective VT (formerly "Vanderpool") and AVT (formerly "Pacifica") technologies.

The core Xen 3.0.2 product can support a single image that can span as large as 32 processors in an SMP setup, which is considerably more SMP scalability than a VMware partition can offer, with only four-core scalability. The latest Xen hypervisor has support for VT and AVT already enabled, too, even though the "Dempsey" and "Woodcrest" Xeon and "Montecito" Itanium chips from Intel and the "Rev F" Opterons from AMD are not yet on the market yet. (To be fair, the dual-core "Paxville" Xeon DP processors have VT support, but these are not exactly volume products with a long life ahead of them.) This paravirtualization is merely a new way to say that because the hardware does a lot of the instruction set virtualization, the hypervisor does not need to, which means you do not have to modify an operating system kernel to use Xen if these VT and AVT features are present. Up until now, to use Xen, you have to tweak the operating system kernel, and that meant it was restricted to open source operating systems or to the vicissitudes of the proprietary operating system providers. With the paravirtualization approach, VT and AVT on X64 chips as well as similar hardware features on IBM's Power chips and Sun Microsystems' Sparc chips, do some of the work. In theory, there could come a day when Xen partitions are supported on all of the major hardware platforms in the world, much as Linux itself is supported on them. And, this stands to reason. (In addition to the Xen 64-bit and 32-bit kernel tweaks for paravirtualization support, there is another Xen tweak called HVM--short for hardware virtual machine--that takes a slightly different approach to virtualization that is even cleaner in that it can support unmodified operating systems.)

But according to Crosby, Xen is about more than Linux, even if it will be one of the key features in Novell's SUSE Linux Enterprise Server 10 distribution (expected in May, with Xen 3.0.2 support expected in the third quarter) and Red Hat's Enterprise Linux 5, due in the fourth quarter. Sun Microsystems is expected to support Xen with its Solaris 10 variant of Unix by the fourth quarter or maybe early in the first quarter, too. And while Microsoft does not yet support the VT or AVT on-chip virtualization features, Xen can work around these limitations, and to that end, a few months ago XenSource quietly licensed the virtual hard disk (VHD) format from Microsoft so it can enable interoperability between Xen and Virtual Server environments. (Virtual Server is Microsoft's own virtualization platform for Windows, which it acquired two years ago and which is expected to get its own hypervisor in 2008 or 2009, perhaps a year or more after Longhorn Server ships.) Crosby would not say how much XenSource had to pay to license the VHD technology from Microsoft, or exactly when the company did it.

"We have consistently said that Xen is not a Linux virtualization platform, and this is a recognition that XenSource is a credible player," explains Crosby. "We do not have any agenda, and customers can use any operating system they want."

So at LinuxWorld this week, you will see XenSource do two things. It will first position itself as a credible, reliable partner with the operating system providers, one with an eight-week software release cycle like many Linux distros have. Perhaps more importantly, Crosby explains, Xen is being implemented in such a way that applications that are certified to run on a native implementation of the operating system running on a real chip will be automatically certified to run on a Xen partition that is paravirtualized on that same chip. In essence, Xen appears as a sub-architecture of the X86/X64 architecture, and in the case of Linux, the Linux kernel will just see Xen as a piece of hardware. "If you are an application provider, you just certify for the software stack, and you are golden whether you run native or virtual," says Crosby. This is, indeed, what customers and software providers need. No one wants to use a hacked operating system kernel and then have to recertify. It isn't the hacking that is the problem--but getting support and certifying the code. All of the hacking is now transparent with Xen.

XenSource will be distributed its Xen hypervisor in conjunction with the Linux distros through what it calls Xen Extensions Packs, which will be integrated with specific implementations and offered with variations aimed at utility computing, high availability, and other special uses. This will be delivered in conjunction with the Linux distros. It is unclear if XenSource will try to establish similar Extension Packs bundles with Microsoft for Windows, Sun for Solaris, and other platforms. The Extension Pack approach is just a recognition that Red Hat customers want Xen integrated and supported through the Red Hat Network and Novell customers want Xen integrated and supported through the Yast Online Update feature of SUSE Linux.

In addition, XenSource plans to sell something called XenEnterprise, which is aimed at companies that want to support multiple operating systems, including Windows and perhaps many different Linuxes. In this case, there is no single support mechanism, and this is what XenSource wants to provide. None of the operating system providers have any desire to support other platforms in their stacks, so someone has to fill this gap. XenEnterprise also includes many of the closed-source features that were once part of a product called XenOptimizer, which XenSource previewed last year. XenOptimizer automates the provisioning of Xen virtual servers and provide fine-grained monitoring and control of processor, memory, I/O, network, and storage resources across networks of servers. Crosby says that the feedback on the XenOptimizer product was good as far as its technology was concerned, but customers told XenSource that wanted it all part of one product. "People are getting tired of being nickeled and dimed to death," he said. No kidding. Exactly how--or if--the XenOptimizer features will be integrated with the embedded Xen hypervisors in Linux distros is not clear. XenEnterprise also includes the so-called P2V conversion tool, which can take a physical server environment, virtualize it, and drop it into a partition in the Xen hypervisor.

XenEnterprise is scheduled for release this summer, with its ramp timed to the deliver of chips with VT and AVT capabilities. And if you have a chip that doesn't support VT or AVT, well, you are just going to have to upgrade. In the long run, software-based instruction set virtualization is going away.