Virtual Desktop Infrastructure (VDI) offers both big promises and big challenges for IT managers. On the plus side, the idea of running some of your desktops inside a secure data center has a lot of appeal, particularly to the generation that grew up during the mainframe computing era and wishes to return back to those simpler days. Data and applications can be better protected, endpoints can be more easily patched, cloned and supported, and users can access their desktop from anywhere there is an Internet connection and a Web browser. On the other hand, the costs for building the right infrastructure can be a real burden and quickly consume the savings that VDI purports to generate.

As an extreme example, a demonstration held at various trade shows last fall by VDI VAR Green Pages showed a very high density of virtual desktops running from a single Cisco Unified Communications switch. Each desktop had over 90 GB of applications, and using a combination of Symantec Workspace Virtualization applications streaming, VMware ESX hosts and VirtualStorm specialized drivers, they were able to run 400 desktops from each of six blades on the switch. “It required a perfect balance between the desktops, the infrastructure, the virtualization and the management of the desktops and their applications in order to scale to thousands of desktops in a single environment,” says Erik Westhovens, one of the engineers from VirtualStorm.com writing on a blog entry about the demonstration.

Let’s look at several challenges to using VDI and some of the lessons that those who are doing well have learned:

— What desktop devices will I use? Whether you end up using thin or thick clients or repurposing older PCs, you probably won’t save on capital cost but on the ongoing operations, support and maintenance costs. “If we have a security breach on a desktop, we just reprovision and it goes away,” says Alan Deloera, the Director of Technology for the city of Temple, Texas.

The number of thin client vendors alone is staggering, from specialized vendors such as Wyse and Priam.com to lines from mainstream computing vendors such as HP and Sun. JetBlue Airlines standardized on HP thin clients and claims to have saved millions in its desktop deployment. Plus, there are different XP-based deployments, including using embedded XP OS called Windows Fundamentals for Legacy PCs.

J&B Group, a food wholesaler and manufacturer based in St. Michael, Minn. decided to migrate its Citrix Presentation Server terminal services environment to a VDI solution “because we wanted a more consistent look and feel like our local XP environment,” says Chuck Ballard, the network and technical services manager at the company. “We also had a lot of complaints with associates not being able to browse their local directories and printers, and the support contracts were getting expensive to renew. They ended up going with Quest Software Inc.’s vWorkspace clients and have begun to deploy this solution to several of their remote office locations to make it easier to support and deploy applications. “We wanted to extend the use of our older PCs which saves us about a $1000 or so per desktop. Also, our support staff doesn’t have to spend time troubleshooting hardware, when we have a problem we just swap out a spare PC and our associates are back up and running quickly. Plus, I don’t need to extend warranties for any of this gear – if one breaks, I just replace it at that time.”

• — How much experience do I have with virtual machine image management and deployment tools? If you have never used virtualization in your organization, now is the time to gain some experience because any successful VDI rollout will need to build on this experience. Each of the major VM vendors offers a series of tools to make it easier to make wholesale changes across your desktop images, so that you can avoid patching individual desktops one at a time. VMware offers vSphere and vComposer, and Microsoft’s System Center has a number of plug-ins to work with Hyper-V and its various VDI elements. There are a number of third-party tools that are worth exploring too, including LiquidWareLabs.com and VDIworks.com.

• –Do I have to beef up my network or storage infrastructure to handle the additional traffic demands of the virtual desktops? One of the issues here is that you have to plan for worst-case scenarios such as the beginning of a workday when everyone arrives at the desk and proceeds to boot their virtual desktop, to ensure that you have enough network capacity to send all these bits down the wire. Some VDI solutions such as Ericom and Synchron don’t require storage area networks (SANs) to start off for smaller deployments. In some cases, with the right deployment of SAN technologies, you can actually save storage costs by deduplicating the virtual images that are stored on them. This is what J&B Group ended up doing with their NetApp arrays, which saved them a lot of storage capacity since most of the VDI images use similar data structures.

• –What remote control protocol will I use between the virtual desktop and the client device? Part of this decision is in understanding your network and the tools that are called connection brokers that determine how to marry a particular remote protocol and desktop host machine. They include such vendors as Citrix Desktop Broker for Presentation Server, LeoStream Virtual Desktop Connection Broker, Ericom, and Quest Software’s Virtual Access Suite. At the University of Rennes in northern France, they made use of the Leostream broker to connect more than 13,000 virtual desktops across campus. They deploy a variety of operating systems including both Windows XP and Linux desktops, and these can boot in a matter of a minute because of the way that they have designed their network. The Leostream broker can also quickly scale up as demands increase for more connections, and integrates with the universities’ single sign-on system. “Our users only have to authenticate once when they connect to our portal,” says Humberto Duarte, the IT Department Co-Director at the University.

— Will my end users be able to access certain legacy hardware that they are used to using, such as graphics or hear audio from their PCs? VDI solutions are notorious in their spotty support for these kinds of applications, and only now just seeing some improvements to provide the same rich experience that ordinary PC users have gotten used to years ago. “For audio and video using Windows Media Player, our VDI solution works fine. But if you are playing a Flash video or using another player it isn’t that good from either our remote desktops or Wyse thin clients,” says Duarte.

Sometimes it can be just a single application that can create deployment problems. Jeff Keith, a senior network engineer with Redlands Community Hospital in California, says that they “initially went with a thin client device at the desktop in order to reduce support costs but ran into a performance issue with a fetal monitoring application. The driver and connection broker client needed on the virtual machine caused high CPU utilization with this application, so we replaced several thin clients with desktop PCs where we were running that application.” Since that decision, they have migrated their VDI solution to a high performance SAN and will replace these PCs with thin clients. “We don’t anticipate any performance issues moving forward. We will continue to evaluate new thin clients and technology as we move forward with our VDI plan.” If your plans call for supporting these applications, make sure whatever VDI solution you evaluate can address this.

• –Do I understand all the various moving parts of my solution? Finally, make sure that you have scoped out your project and detailed all the various parts that make up your VDI implementation. For example, Microsoft’s VDI solution requires four different Remote Desktop servers (the Virtualization Host server, the Connection Broker, the Remote Desktop server itself and Remote Desktop Web Access server). While these can run concurrently on a single piece of hardware, there is still a lot to keep track of. Microsoft also requires specialized licensing called the Windows Virtual Enterprise Centralized Desktop license in addition to standard enterprise licenses to further complicate matters. VMware’s VDI solution is just as complex with a number of different products that have to work together. This is where having a specialized VDI VAR can come in handy.

One alternative is to investigate a “starter kit” or bundle that various vendors have assembled to make deploying VDI easier. Notable products here include HP, Ericom, Synchron and Quest Software. “We looked at a couple of others but Ericom’s ease of use and technical support and Microsoft integration were big reasons we went with them,” says Larry Pickard, the director of IT for the San Francisco Theological Seminary. The seminary is using 80 VDI clients with a combination of HyperV, System Center and eventually Wyse thin clients.