During Citrix Synergy 2009, the company announced Citrix XenClient, the technology many of us remember as "Project Independence" developed in collaboration with Intel. For end-users, perhaps the most interesting thing to note during its announcement was the price tag: free. Much like the company's server virtualization hypervisor technology, XenServer, this newly dubbed client technology will also be given away for free. And after seeding the market, Citrix should be able to make money with add-ons and management applications. Or at least, that seems to be the claim to fame at this moment. Makes sense to me.
So what exactly is it, other than client-side technology? Citrix XenClient, as you may have guessed from the name, is a Type-1 native hypervisor that operates on top of a client device such as a desktop or notebook PC -- it is a virtualization hypervisor that operates on bare metal. With it, you can then host one or more guest operating systems. This is akin to the server virtualization technology that you have become all too familiar with such as VMware ESX, Microsoft Hyper-V, or Xen. The technology promises to offer faster and more secure virtualization environments than today's offerings.
So don't confuse this technology with the Type-2 or hosted hypervisor technology that has become quite popular on current client machines. Examples of this technology are VMware Workstation, VMware Fusion, Microsoft Virtual PC, Parallels Workstation, or Sun's VirtualBox. These virtualization platforms install on top of a hosted operating system, like Windows, Linux, or Mac OS X. And they typically suffer from a performance penalty due to the added layer of abstraction and the underlying host OS.
With XenClient, Citrix has decided to take what could be argued as the more difficult path of client virtualization, or at least the road less travelled. However, it isn'tt the only company going after this space. As the current virtualization giant in the industry, VMware made a similar announcement to XenClient during its own trade show, VMworld Europe, back in February. VMware and Intel announced their own collaboration as they work toward another client hypervisor. There are also startup companies in this space, such as Neocleus and Virtual Computer, both of which have produced their own Type-1 client hypervisors.