Yet another variation is to combine application streaming with terminal services. At Alamance Regional Medical Center in Burlington, N.C., senior network administrator Andy Gerringer uses both Citrix and SoftGrid to provision desktops. Citrix is used in the usual manner to deliver server-based applications as individual sessions. But Alamance also uses Citrix to provide access to a SoftGrid desktop environment for terminal users. Essentially, the Citrix session runs the SoftGrid virtual machine. "SoftGrid and Citrix complement each other very well," Gerringer says.

Conflict resolution for applications

Application streaming comes with a significant side benefit: eliminating application conflicts. The application streaming tools from AppStream, Altiris, and Microsoft separate application-specific support files such as DLLs and libraries from the underlying operating system. Altiris separates just the support files, keeping the applications with the operating system, whereas AppStream and Microsoft keep each app and its support files together in one virtual layer or package.

These programs manage the communication among the layers and the underlying operating environment, so both Windows and its users think they are working on a single environment. By separating each application into its own virtual layer (or package, as some call it), these products prevent software conflicts common with homegrown software and some commercial applications. And user-installed applications can't conflict with IT-provisioned applications in the virtual layers, says Microsoft's Grescher.

For example, before adopting SoftGrid, recalls Alamance's Gerringer, the medical center had to maintain separate servers for ill-behaved apps, forcing users to switch among multiple systems from their terminals. "By summer 2005, the problem got too big to manage anymore the old way," Gerringer says.