Client Hypervisor Technology
Published: May 10, 2010
Virtualization through the use of hypervisors on the server has clear benefits, including consolidation, power savings, and better utilization of the information technology (IT) infrastructure. As a result of these well-documented benefits, IT professionals naturally want to investigate the potential of using hypervisors on the client.
This article examines client hypervisor technology with regard to scenarios in which hypervisor technology might be relevant (for example, isolation) and recommends virtualization alternatives for other scenarios. In this article:
What is a Client Hypervisor?
A client hypervisor, also known as Type I or bare-metal virtualization on the client, creates a virtualization layer that runs directly on the hardware. This layer runs one or more operating system instances, which it virtualizes to some extent. A client hypervisor differs from the more common Type II client virtualization, in which the virtualization layer runs as an application on the Windows operating system and enables additional instances of a virtual operating system. Windows Virtual PC is an example of Type II virtualization.
Environment isolation is a common situation for which customers consider client hypervisors. In this scenario, customers run multiple, isolated computing environments on a single device and partition those environments based on security levels. Client hypervisors address this scenario well by running—and isolating—multiple instances of Windows on the same device. However, virtual desktop infrastructure (VDI) can also address this scenario and offers a higher level of separation and data security. VDI keeps the data and the applications in the datacenter and provides the user a view of the desktop only.
Although hypervisors can make sense when users need more than one operating system instance on their desktop computers, some vendors also claim that client hypervisors can enable hardware independence and eliminate device-driver complexity. Hardware independence appeals to IT pros, who want to simplify deployment, maintenance, and support by deploying a single image for all desktop computers.
Thinking through this solution, a client hypervisor implementation that abstracts Windows from the hardware must provide drivers and support for all types of devices. Developing drivers for the variety of devices that Windows supports is a complex endeavor. To avoid this complexity, vendors need to do one of the following:
In contrast, Windows provides a high level of hardware compatibility. The Windows driver ecosystem has matured and stabilized over the years. Windows has a huge install-base and development community. Most devices work out of the box, and driver installation occurs within minutes during deployment. In larger deployments, additional device drivers can be installed from the network or Windows Update.
Simplifying Windows Deployment
An extension of the hardware-independence claims for client hypervisors is that IT pros can simplify Windows deployment by using client hypervisors to reduce image count.
Synchronizing Multiple Desktops
Vendors often mention client hypervisors in the context of offline VDI. By definition, VDI is a remote desktop: an online, well-connected experience. Trying to achieve offline VDI is about enabling the same rich user experience on a desktop, whether the user is online or offline and inside or outside the corporate network. The most cost-effective way to achieve that goal is simply to use a laptop—a one-stop solution for all those needs with the best user experience, anywhere.
To summarize: Some vendors recommend a client hypervisor on laptops, to facilitate synchronization with a VDI desktop so that you can rapidly copy a desktop from the server to a client and vice versa. IT pros should evaluate whether they need to support such a scenario. They should also evaluate whether deploying a new, early-stage virtualization solution for all their laptops and synchronizing the operating system image between a local device and VDI storage makes more sense than simply synchronizing user files, settings, and applications.
One Device for Work and Personal Life
Users tend to use corporate laptops for personal purposes as well as for business, or they use their own laptops or home computers for work. Using a client hypervisor to enable this scenario is attractive to some organizations: Users can maintain work and personal environments on one device but can keep them separated, from a management and support perspective. Users can install any application they want in their personal environment, while the corporate IT department manages and controls the work environment.
Additionally, a client hypervisor complicates installation and usage. Installing a hypervisor on user computers limits their hardware choices because a hypervisor requires more memory and specific CPU virtualization capabilities. Moreover, installation is intrusive and changes the boot process, so an IT pro must manually configure devices.
Development, Test, and Demo
For a long time, customers have used Type II virtualization technologies such as Windows Virtual PC to run multiple environments for development, test, evaluation, and demo purposes. As Type I virtualization becomes available on the client, it will become a relevant solution for developers, test engineers, and sales people who need to use multiple operating system environments. Type I virtualization could have the benefits of running the same type of virtualization on the server and the desktop, being able to easily debug or demonstrate server environments on desktops, or loading test environments from the desktop to servers.
Desktop virtualization is a proven mitigation strategy for application-compatibility issues. With this strategy, IT pros provision their users with a previous version of Windows in a virtual machine, to support incompatible applications.
IT pros who need more than one operating system environment on a desktop computer should consider virtualization. When isolation is also required (for example, in high-security environments or when separating work and personal activities on a corporate laptop), IT pros might consider either a client hypervisor or VDI. If a user requires remote access but is not provisioned with a corporate laptop, VDI might be the better option.