Though Citrix has released an early version of its bare-metal client hypervisor, XenClient, the technology is still a work in progress, with about 30 known issues that require workarounds.
The release-candidate (RC) version of XenClient is feature-complete and is available for download as part of the XenClient Express Test Kit, which comes with a receiver and synchronizer to connect users to XenDesktop. The RC was released at Citrix Synergy 2010, the company's annual user conference held in San Francisco this week.
As reported last week by SearchVirtualDesktop.com, XenClient will provide offline support for virtual desktops when the final release is available in the next version of XenDesktop, either later this year or in 2011. Citrix did not provide details on pricing or availability.
Geert Braakhekke, a freelance IT consultant for Citrix and VMware products, won an HP notebook PC with XenClient during a hands-on lab at the conference. He said he likes XenClient because it lets him switch between different operating system environments with good performance -- but it's no replacement for XenDesktop.
"It's a good feature for road warriors," he said.
XenClient RC is far from complete, though. According to the product-release notes, workarounds are necessary for over 30 problems -- five high-severity, 14 medium and 17 low.
One high-severity issue is that after a guest OS resumes from suspend mode, USB drives are unavailable. Another problem is that attempts to authenticate with Active Directory through Citrix receiver for XenClient may fail, and a medium-level issue is that shared applications aren't removed after deleting a virtual machine.
One analyst also pointed out that XenClient has full time backup and rapid recovery, but that recovery is image-level; file and object-level recovery would be ideal.
Citrix will probably smooth out most, if not all, of these problems before reaching general availability. In the end, however, a client hypervisor won't be for everyone.
Jim Sanzone, a server and desktop virtualization consultant at a New York-based IT services company, said a bare metal hypervisor such as XenClient is great for company-owned machines, but it "takes over the whole machine," so end users may not want it on their personal devices.
"Think about deprovisioning when the company and employee part ways, and also support of the device if the company doesn't own it," Sanzone said. "There's a lot to think about."
Microsoft's stand on client hypervisors
Microsoft advised against using client hypervisors in certain scenarios on its Windows blog this week. The company's stand is that client hypervisors are useful for corporate users who need more than one work environment, but it doesn't make sense for end users with basic needs.
"A client hypervisor can add complexity, particularly as it requires premium hardware, with virtualization capabilities in the CPU and BIOS, usually additional RAM and management," Microsoft said on its blog."The deployment also tends to be more demanding and can require additional management and patching to keep it up to date. This is because it's installed beneath the OS, and so standard software distribution mechanisms do not support this."
Of course, it makes sense for Microsoft to discourage the use of Type 1 client hypervisors which disrupts Microsoft's status quo by running below Windows and abstracting it from the hardware.
And the good outweighs the bad for mobile virtual desktop infrastructure users because the technology offers a way to access virtual desktops while offline.
"A 'caching client,' if you want to call it that, for traveling devices is very much in demand during architectural discussions. It comes up pretty consistently when we discuss executive laptops," said Luke Wignall, vice president of Denver-based IT services firm Common Knowledge Technology LLC. Plus, he said, "IT loves the idea of having such a fresh build on every reboot for their demanding C-level execs."
VMware is also working on a client hypervisor, but it put development efforts on hold in favor of "client-mode," a Type 2 hypervisor that will provide offline support for VMware View 4.5 when that product hits sometime this year. VMware said pricing will be the same as the previous version.