Over the past few years companies of all sizes have begun to examine the resource utilization and efficiency of a distributed desktop environment -- and they've discovered such an architecture is not efficient. Instead a server-centric, managed, terminal environment offers many economic benefits, which they leveraged through Citrix technologies.
The market for Citrix partners has been favorable as companies have moved back toward server-based computing; businesses have had success publishing their commercial off the shelf software (COTS) on Citrix servers and allowing ICA clients to connect to the applications. However, not all applications can be run in a terminal environment. This may be especially true with custom applications developed in house.
To address application compatibility problems, businesses may use a technology like VMware's Virtual Desktop Infrastructure (VDI). With VDI every thin client connects to a separate operating system instance running on VMware ESX Server, rather than connecting to an application instance running on the same operating system as Citrix.
This an ideal solution to implement when applications that won't work in a terminal environment prevent the move to a server-centric infrastructure. But it leaves Citrix resellers without a market opportunity for these businesses. Or does it?
Citrix has taken an "if you can't beat 'em, join 'em" attitude toward virtualization technologies like VDI by offering a complementary product: Desktop Broker for Presentation Server. Available as an add-on to Citrix Presentation Server, this product is free to Presentation Server customers who have active Subscription Advantage support contracts. In a nutshell, the Desktop Broker manages the connections to virtual machines that may be provided by a VMware VDI offering. The client device uses Citrix's ICA protocol to connect to the Desktop Broker server, then the Desktop Broker server acts as a middleman to connect to a Windows XP virtual machine using RDP. Essentially each client connects to a separate Windows XP virtual machine through a "double terminal" session.
You may think a double terminal session to access a virtual machine would degrade performance. However, the Tolly Group's hands-on assessment of a Citrix virtual environment showed it can be architecturally sound, providing 200 simultaneous user sessions for light workload users and 175 simultaneous user sessions for heavy workload users on one Presentation Broker server.
So what's the market opportunity for Citrix resellers? The Desktop Broker for Presentation Server is the first component in what Citrix is calling The Dynamic Desktop Initiative, to deliver on-demand desktop environments to the workers that need them. Citrix takes a tiered approach to on-demand desktop delivery. Workers who use applications that can run in a terminal environment should connect to desktops through traditional ICA terminal sessions. Workers who use applications that cannot run properly in a terminal environment or who need to personalize their desktops should connect with a Desktop Broker/VDI combination, providing them with isolated Windows XP sessions. This tiered approach creates a best-of-breed solution for businesses wanting a server-centric environment. They use a combination of traditional and VDI depending on departmental needs – and you can help them set it up. This can be more economically viable than a straight VDI solution as well.
Even if a business has no need for VDI, virtualization technology like VMware can still be leveraged to virtualize the ancillary servers that are required for a robust Citrix environment. These virtualization targets could be servers like web servers and xml servers. You may even be able to virtualize some of the actual Citrix application servers if they have really light loads as standalone servers. Virtualizing application servers may be useful if you have to create application silos due to application conflicts caused by incompatible applications being installed on the same server. Instead of installing the applications on separate physical Citrix servers, you might be able to install the applications on separate virtual Citrix servers running on the same hardware. This will not work in all scenarios, but in light load situations it may be feasible.
Virtualization technologies like VMware should be viewed complimentary to Citrix, rather than competing products. Citrix resellers can use it to virtualize ancillary servers in a Citrix solution. They can also leverage the Desktop Broker for Presentation Server in order to offer some value to customers who may not be able to run their applications in a terminal environment. With the Dynamic Desktop Initiative, Citrix is pushing to deliver on-demand desktop environments to workers. This initiative cannot be realized without some form of virtualization technology. If Citrix sticks to the Dynamic Desktop Initiative, machine virtualization and Citrix may have a bright future together.
About the author: Harley Stagner has been an IT professional for almost eight years. He has a wide range of knowledge in many areas of the IT field, including network design and administration, scripting and troubleshooting. Of particular interest to Harley is virtualization technology. He was the technical editor for Chris Wolf and Erick M. Halter's book Virtualization: From Desktop to the Enterprise and currently writes his own blog at www.harleystagner.com. Ask Harley your server virtualization questions today.