Citrix continues to press its interest in the desktop virtualisation space, after it was revealed that it has invested in a start-up called Virtual Computer, which has only recently exited stealth mode.

Citrix has spent the past year and a half redefining itself as a virtualisation company, first purchasing the desktop and server virtualisation vendor XenSource and then placing the "Xen" name on its flagship application delivery software to reflect a focus on virtualisation.

Virtual Computer was founded in November 2007, in order to focus on the provisioning, publishing and patching of desktop and laptop operating systems. Virtual Computer, whose NxTop software is in beta and is based on open source Xen software, exited stealth mode in September and it has emerged this week that Citrix is a key investor.

At a time when venture investment in the IT industry has hit its lowest point in a decade, Virtual Computer has snagged $15 million (£10.6 million) in a funding round led by Highland Capital Partners and Flybridge Capital Partners.

Citrix contributed an undisclosed but "significant" portion of the $15 million, says Virtual Computer CEO and co-founder Dan McCall. Virtual Computer previously secured $6 million from Flybridge and Highland early in 2008.

"This is an interesting and exciting young company and we have a shared vision about what's going on in the space," says Andy Cohen, Citrix's senior director of strategic development. "We think it's important to help support people who are coalescing around Xen-based technologies."

When asked if this might be the first step toward acquiring Virtual Computer, Cohen said, "We own a small percentage of them now. Because of the shared vision ... that's certainly a possibility."

Although Citrix and Virtual Computer both make desktop virtualisation products and could potentially compete against each other, Virtual Computer is going after a part of the market that Citrix has not yet addressed, Cohen says.

Virtual Computer's NxTop software is a bare metal, or "Type 1" hypervisor, whereas most desktop virtualisation products are "Type 2" and thus run on top of an operating system, McCall says. Type 2 hypervisors are sometimes vulnerable to various security, management and performance problems, according to McCall.

NxTop creates a layer of independence between the hardware and operating system. The software allows central management of PCs just as other virtualisation products do, but McCall says Virtual Computer provides a "loosely connected" model in which PCs can be easily customised and run smoothly even when disconnected from the central server.

NxTop pushes a base operating system image out to desktops and laptops, and then customises individual devices by adding from a list of optional applications. Patches are delivered centrally, but if a patch fails then each device's desktop image automatically rolls back to the previous version to prevent downtime.

Although Virtual Computer relies on virtualisation software, the company is describing itself more broadly as a PC life-cycle management vendor.

"In the centralised server, you create one operating system," McCall says. "We try to make it as easy to manage 1,000 computers as it is to manage one."

Citrix currently does not offer a Type 1 or Type 2 desktop hypervisor, instead using a server-based virtual desktop infrastructure, which is completely centralised and streams the entire virtual machine out to clients, Cohen says.

However, Citrix recently began collaborating with Intel to create a Xen-based Type 1 desktop hypervisor, which would be more along the lines of what Virtual Computer has developed.

Virtual Computer's software can virtualise Windows and Linux, letting multiple operating systems run on the same desktop. The vendor's product does not work on thin clients, and does not work with Macs because of licensing issues.

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