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Bare-metal desktop hypervisors: A primer

Client virtualization holds long-term potential but is in its infancy

By , Network World
July 22, 2010 02:36 PM ET

Network World - Desktop virtualization is hot -- ask any IT pundit. But it can also be confusing, because the market contains a variety of server- and client-based technologies for creating virtual desktops.

Virtual desktop infrastructure (VDI) may be the best-known model, but a new entry into the desktop virtualization mix is the bare-metal desktop hypervisor. Proponents say bare-metal will revolutionize the world of corporate PCs, with desktop images that are secure, portable, and offer offline access. But the technology is in its infancy -- even big players such as Citrix and VMware are struggling to get bare-metal hypervisors out of the conceptual phase and into production.

Desktop virtualization

This article will explain what bare-metal hypervisors are, which vendors are making them, and why they are different from previous virtual desktop technologies.

What is a bare-metal hypervisor?

Simply put, the bare-metal hypervisor, also known as a Type 1 hypervisor, is virtualization software that is installed directly onto the PC's hardware. A Type 1 hypervisor controls both the hardware and one or more guest operating systems. A machine running a desktop hypervisor could run multiple operating systems, but there are benefits even when only one operating system is required.

How is this different from existing types of desktop virtualization?

Today's client hypervisors -- such as VMware Player, Parallels Desktop and Windows Virtual PC -- are of the "Type 2" variety, meaning they are not installed directly on the machine's hardware. Instead, they run within the computer's host operating system, allowing guest operating systems to run in a third layer above the hypervisor and native OS. While Type 2 hypervisors have control over the virtual desktop images installed on the computer, the underlying hardware is still directly managed by the host OS, whether it be Windows, Linux or Mac. Type 2 desktop hypervisors are typically used by IT in test and development, rather than for business-wide virtual desktop deployments, Burton Group analyst Chris Wolf says.

Virtual desktops can also be created without installing hypervisors onto user devices. In the server-hosted model, commonly called VDI, desktop images are hosted on servers inside the data center, and accessed remotely by laptops, desktops and thin clients. This model may involve use of a server hypervisor, but the desktops themselves would need only a method for accessing the virtual machines, such as a web browser or a light software client.

Which vendors make bare-metal desktop hypervisors?

Start-ups Virtual Computer and Neocleus are shipping bare-metal hypervisors today.

Citrix has unveiled a test version of its bare-metal hypervisor, known as XenClient, and says major PC vendors will ship new desktops with the hypervisor pre-installed. But it's not clear exactly when that will happen.

Citrix's hypervisor was originally due out last year, and while the product was plagued by delays Citrix is still ahead of rival VMware, which was promising a hypervisor last year and now says there is no timeline for the release.

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