InfoWorld review: Desktop virtualization made easy

The virtualization in VDI

One key difference among the solutions is the choice of virtualization platform. Both Kaviza and Pano Logic sit on top of a bare-metal hypervisor, or Type 1 virtualization infrastructure, which hosts both the management component and the desktop virtual machines. Pano Logic includes the VMware or Microsoft virtualization infrastructure as part of the bundle, while Kaviza requires an existing virtualized infrastructure (either VMware or Citrix XenServer). NComputing, on the other hand, provides its own form of virtualization, called vSpace, which is more akin to Terminal Services than VMware, Hyper-V, or XenServer. NComputing's vSpace is an application that needs only a Windows XP Pro or Windows Server 2003 box to run on, allowing up to 30 concurrent users on basic, off-the-shelf hardware.

When choosing among Kaviza, NComputing, and Pano Logic, the question becomes one of virtual machines versus a shared operating system environment for the end-user desktops. With Kaviza and Pano Logic, you can create different virtual machine images for different user profiles. With NComputing, all users run the same OS and applications as the host. In return for the generic user environment, both hardware and administrative requirements are lower.

Like a lot of IT hot-button topics, some admins feel strongly about one flavor of virtualization versus another. During my tests, I had no problems with any of the VDI solutions. While I only scaled up to 10 concurrent users, all three performed well and none gave me any indication that I was in jeopardy of running out of resources. (For more on Terminal Services and thin client computing versus VDI, see InfoWorld's Thin Client Computing Deep Dive and VDI Deep Dive reports.)

Personalizing virtual desktops
One of VDI's more interesting features is on-the-fly creation of clean virtual machines from standard images as users log on. By deploying nonpersistent desktop VMs, there is no chance of permanent damage from viruses, malware, or user error. To bring each user's personal settings to these dynamic desktop VMs (or to each user session, in the case of NComputing), the three solutions all take advantage of Active Directory roaming profiles.

Roaming profiles are one of the oldest ways to provide user personalization on Windows-based networks. Through Active Directory group policy, a user's personalization information is collected from the local profile and stored on a server somewhere in the domain. This stored profile includes the My Documents folder, Outlook email settings, printer assignments, desktop icons, and other settings that make the desktop environment unique to the user.

The roaming profile is part of the Windows user identity and independent of the underlying system. That means a roaming profile will provide the personal user settings to any Windows device in the domain: a physical desktop, virtual desktop, or Terminal Services user session. The profile is applied during the logon process, and any changes made during the session are saved on logout. Roaming profiles are not fancy, but they are very effective at giving the end-user the perception of a persistent desktop when in fact the virtual desktop is newly created upon each logon.