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Will Citrix OS Streaming Deliver Vista Or Linux?

Citrix's announcement Wednesday that it would buy virtualization vendor XenSource for about $500 million in cash and stock has been generating a great deal of buzz. The announcement clearly indicates Citrix's desire to become a power player in the virtualization market, but the purchase could have a bigger impact on the desktop than the server.

Right now, hypervisor technology is mostly confined to the data center:
Server virtualization is how Wall Street justifies VMWare's valuation,
and where Citrix expects Xensource's revenue to come from for the next
two years. But in the long term, OS virtualization on the desktop (or
laptop) is potentially a bigger market, and a closer fit to the existing
Citrix product line.

Citrix has traditionally been about thin clients, a technology
increasingly marginalized thanks to its need for a LAN connection ---
something often absent as office-bound desktops make way for mobile
laptops. Citrix's response so far has been application streaming, which
improves on thin clients in the same way that Ajax improves on static
Web pages. Apps run locally on a PC so that they can take advantage of
its hardware but they're not installed on it. Instead, Presentation
Server and competitors from Microsoft, Symantec, and LANDesk keep track
of all the DLLs, registry changes, and other settings that
each application requires, giving each one its own virtual registry
that's cached on the client PC hard drive for offline use.

This kind of virtualization lite can avoid application conflicts, but it
doesn't help when the problem is with the OS itself: If one app only
runs on Vista and another will only run on XP, registry tweaks won't get
them working together. In April, Citrix announced its solution, Desktop
Server, but this is essentially just a rebranded thin client. One OS
(usually XP) runs locally, while another (usually Vista) runs centrally
and is accessed via a LAN

Though Citrix won't talk about plans for future products that integrate
XenSource technology, it has mentioned OS streaming, which would entail
the Xen hypervisor as well as provisioning technology acquired with
Ardence in 2006. Citrix also is working with Microsoft on a
paravirtualized version of Windows, meaning one that's optimized to run
on the Xen hypervisor. While new hardware from Intel and AMD -- now in
most desktops and laptops, not just servers -- means this optimization
isn't strictly necessary, it still boosts performance.

Paravirtualized Windows is so far confined to the server, but Vista is
based on the same Longhorn codebase as Windows Server 2008, so porting it
to the desktop would be relatively easy. The big question here is
whether Microsoft will want to encourage running Vista on an open-source
hypervisor rather than its own Viridian. That will depend on how far
Viridian gets beyond the vaporware stage, as well as the exact license
adopted by the new consortium to which Citrix plans to hand over
responsibility for free Xen. Microsoft would likely reject any
client-side code released under GPL v3, thanks to a clause forbidding
use in any consumer hardware that uses digital signatures to prevent
users loading their own software.

XenSource could strain the Citrix-Microsoft partnership in other
ways, all of which are good for enterprise IT. For example, Intel's vPro
technology puts management and security software for XP or Vista in a
separate OS. Early versions use Windows CE as the other OS, but in May
Intel announced a partnership with Red Hat and a move to Linux. Earlier
this month, Dell showed off a business desktop that used Xen to run
Windows and Ubuntu together. The biggest winner is likely to be Apple.
Whereas application streaming only works with Windows, OS streaming will
let users explore other options.

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