Is the traditional use of Terminal Services dead? More specifically, is the Citrix application presentation or desktop publishing method now an outdated way of providing resources to users?

When Terminal Services was first created it was a good way to provide central management of software resources and applications for users. Especially users who worked in a low bandwidth environment. It was also a good way to share resources and lower operational costs.

The improvements Citrix Presentation Server and Xenapp layered on top of the Windows Terminal Services has greatly enhance the functionality and offerings available to clients. But there has always been issues, ranging from niggling little annoyances to big functional problems.

These problems include:

  • session sharing issues
  • printer drivers and spool issues
  • software compatibility
  • resources limitations
  • perceived and real performance issues
  • fairly poor user experience

Until recently Terminal Services has still been the best way to deliver centrally controlled applications and sharing resources.

When Virtual Desktop Interfaces (VDI) were introduced some organizations shifted pretty quickly to this as an alternative to Terminal Services. The problem with this was that the cost was the same or more from a licensing point of view. It also did not scale as well as Terminal Services. You could only get about 20 virtual desktops on a virtual machine host, depending on the hardware used.

The delivery was clunky, at best, and relied on the Microsoft RDP protocol or some licensed hybrid version of it. VDI’s require disk space and a fare bit of it. If you had 20 Windows XP virtual guests you would need approximately 200 GB of disk space. Based on 10 GB per machine.

Each virtual machine would also need patching and updating on an individual basis. If you were using the Enterprise version of VMWare Virtual Infrastructure you could clone the virtual machines, but the overall management was effectively the same as dealing with physical desktops.

The basic VDI Problems were:

  • scalability
  • cost – server, SAN and Virtualization Software Licensing
  • Licensing for Vista
  • Disk space requirements

Citrix XenDesktop 2.1 is the latest version of its desktop virtualization software. It is combined with XenServer, Citrix Provisioning Server and a limited version of XenApp. The key benefit of this software over other virtualization products is the Citrix Provisioning Server, formally called Ardence. The benefit of Citrix Provisioning server is you can now use a single image to run several virtual machines. This dramatically simplifies resource requirements and workstation management.

If you need to update the master image, simply boot the template machine in private mode and update it. Then convert it back to a standard shared image. VMWare is also bringing some similar functionality to its VDI products in the future.

With Citrix XenDesktop a web interface is built into the installation. You can access your virtual desktop using a desktop client or via a web browser and web plugin. Is this a better way to provide access to software and resources? A few months ago I would has said no, I now think it is.

When using VDI the traditional issues of operating within a Terminal Service environment are removed or reduced. You do not need terminal service aware print drivers because you are not sharing, performance is generally increased. Resources are shared still but on the virtualized hardware. This means that you are still getting effective use of your hardware.

The scalability issues are being reduced because of the Provisioning server style disk usage and the increasing capability of server hardware.

If you want to implement Vista the license costs are still very high and you have to jump through a couple more hoops as well. You need Software assurance for you Vista machines and VECD licenses with Software Assurance for each Vista virtual machine.

If you needed to implement a centralised management of software and resources would you be better to implement Terminal Servers or VDI? I think with the Citrix XenDesktop 2.1 offerings and other similar players technology, it would be better to implement a VDI solution.

This will depend on a few factors, but in general if I was to start over right now I would implement VDI for remote access and selected applications and streamed applications for physical desktops. This way IT can manage applications centrally and the end user can have improved performance.

 

What do you think? What are your experiences?