Application virtualization is becoming increasing popular. Many vendors are releasing, or have released, application virtualization utilities. Microsoft has SoftGrid, Altiris has SVS, and Citrix has their Application Streaming Client. Application virtualization can be used in conjunction with other technologies such as Citrix XenApp / Terminal Services, Citrix XenDesktop / VMware VDI, or simply workstations you may already have rolled out to your end users, especially Windows Vista.

We’re going to focus on VMware ThinApp and Citrix XenApp, but these benefits would also be applicable to a virtual desktop infrastructure as well.

First, ThinApp applications require no agent software to be installed, can run without administrative permissions and can run from any network share so it’s easy to maintain.

Second, ThinApp’s virtual OS (VOS) consumes little system resources. In fact, the VOS should consume no more than 400k of disk space or 2mb RAM per each instance running, thus keeping the majority of system services free for Citrix processes.

Third, ThinApp runs entirely in User Mode, there are no kernel mode components/device drivers. This provides a multitude of system stability and security benefits, in that it reduces the impact of any performance issues or security breaches. This concept should be familiar to Citrix Administrators, especially when thinking about user and kernel mode printer drivers. If there is a problem with a user mode printer driver, a specific print queue is affected. If there is a problem with a kernel mode driver, the print spooler service typically crashes, disrupting printing for each user connected to the Citrix server.

Fourth, you don’t install applications on the Citrix server, you merely publish the ThinApp packages. This, in effect, eliminates application conflicts! It eliminates “DLL Hell”! This is so exciting! You don’t have to worry about the consequences of installing ApplicationB when ApplicationA is already installed. You don’t have to worry about the impact on ApplicationC when updating ApplicationD. Multiple versions of applications, such as Microsoft Office, can be virtualized and published on the same Citrix server so easily, and they won’t fight with one another. I could go on and on, but I hope the point has been made.

Finally, virtualizing your applications with ThinApp will reduce application rollout time, the cost of maintaining your Citrix servers, and will likely reduce the number of Citrix servers you require. By eliminating the application “drag” on the Citrix servers, the majority of system resources are free to service end user connections, thereby increasing the number of ICA connections supported by each server.

I encourage each of you to consider application virtualization to build a high-performance Citrix Server Farm.