Citrix: Building strong virtual desktops six ways

Citrix's announcement of XenDesktop 4 this week came with a few interesting twists.

The announcement went over several new features such as HDX, a technology that allows better performance of high-end graphics on virtual PC clients. But what's most interesting is XenDesktop's ability to orchestrate the delivery of array of different virtualization options to meet user needs.  

XenDesktop 4 brings all of Citrix's client virtualization schemes (including XenApp, formerly Presentation Server) under a single management umbrella called FlexCast. From an iPhone to laptops to call center thin PCs, Citrix can be configured to deliver different virtualization technologies to different end points and determine which is appropriate for a requesting user based on the context: (The user's role, location and device type). Pulling off this ability to intelligently detect the user and device type, context (inside or outside of the firewall) and provide the correct delivery mechanism on demand requires both end point device analysis and policies that the administrator must set on the back end. FlexCast can also recognize that the form factor (display) is different for a given device and adjust for that as well, says Calvin Hsu, director of product marketing.

For example, a user logging in from a corporate desktop might get a different delivery mechanism and security profile from a personal laptop coming in over an unsecured connection. "There are policies you can set on the server side and integration with our Access gateway solution that enable you to take some of that end point analysis and leverage it," Hsu says.

Have it your way: Six approaches to desktop virtualization.

What, exactly, are the desktop virtualization options that Citrix is delivering? It offers five virtualization schemes today, and has a sixth in the works.

1. Hosted shared apps or desktops. The former is the classic Citrix XenApp/Presentation Server "thin client" approach. Applications run on hosted servers and keystrokes and screens are exchanged with the desktop. No personalization. Citrix says users can get up to 500 users per server using this cookie-cutter approach to desktop application delivery. The latter uses the same technology to deliver a complete virtaulized desktop environment. Applications are layered on top of that, as is a "personalization layer" that remembers the user's desktop configuration settings such as wallpaper and the placement of desktop icons.

2. Hosted VM-based desktops. This is the model popularized by VMware's VDI (since rebadged as VMware View). Each desktop has a complete, non shared operating system environment running as a virtual machine on a back end server. It offers more personalization and the environment can be isolated from other users or environments running on the same machine. Citrix claims administrators can get 50-60 users per server. Citrix hopes its customers will use this approach to smooth migrations to Windows 7.

3. Hosted blade PCs. Every user has a dedicated PC blade in the server room - no shared system hardware on the back end. Designed for high performance workstations (3-D, CAD, GIS) that need more horsepower than a shared XenApp host can deliver. There's not much of a consolidation benefit here and no shared resources, but the scheme does provide for easier configuration management.

4. Local streamed desktops. The desktop boots from the network, receives the system image as a bit stream over the network and executes it locally. To speed operations, the streamed code is prioritized so that the operating system and applications may begin running before the full system image is downloaded. The benefit is a centrally managed "golden master" system image that users can't screw up. Each time the user reboots a new, clean system image is delivered. One typical use environment: A school computer lab. A few hundred desktops can be supported from one streaming server using this method.

5. Local streamed applications. This approach, popularized by Softricity (now Microsoft's App-V), streams individual Windows applications to the user's local Windows desktop. The streamed applications run in an "encapsulated" environment that's protected from the rest of the user's Windows environment. Streaming is optimized so that applications can run before all of the application code is downloaded, and it can be cached locally to improve performance. One benefit: It speeds the deployment of new applications by eliminating the need for extensive regression testing for every Windows configuration. It also allows two incompatible versions of the same application to run side by side.

6. Local VM-based desktops. Delivery of a complete desktop environment, encapsulated in a virtual machine that lives on the user's PC or laptop but is still remotely synchronized and managed from the data center. The VM environment is completely isolated from the local client's operating environment. This approach offers security benefits for providing access to unmanaged personal laptops, desktops or other devices. "No one wants to carry around multiple laptops, one for them and one for business," Hsu says. In this way, the corporate image can piggy back on the user's personal machine, yet be completely isolated from it for security purposes.

This is the one area where Citrix does not have a product, however. "It's an emerging technology [that's] not yet available," Hsu says. He did not give a time frame for delivery of the capability.

For more details on the announcement and pricing, see Computerworld's XenDesktop 4 story.