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Checklist: Key factors in planning a virtual desktop infrastructure

Before you dive into desktop virtualization, you'll need to understand what you can do with this technology, and what your limits may be Learn more in this tip by Anne Skamarock.

You have heard many people, including me, promote virtual desktop and application virtualization implementations...

for good reasons: Virtual desktop and application virtualization can increase desktop security, reduce desktop and application management responsibilities and reduce calls to your service desk. However, like all smart shoppers, buyers must be aware of what they are getting into. This checklist explains some of the possible environments where desktop and application virtualization may pose some challenges.

  • Delivery options
    Today, desktop virtualization and application virtualization give IT a broad range of delivery options. For instance, hosted desktops and applications using Microsoft Terminal Services or Citrix XenApp can be the delivery method. Other options include application virtualization (known as isolation or sandboxing) and application streaming with products like Citrix XenApp, Microsoft App-V, Symantec Altiris SVS or VMware ThinApp and virtual desktop delivery using a virtual desktop infrastructure (VDI) with Citrix XenDekstop or VMware VDI. They all provide IT and end users with a range of performance and flexibility options. For example, using hosted application virtualization with XenApp has the greatest consolidation ratio for delivering applications and desktops to users, but of all the options, it has the most limited performance capabilities.

  • Costs
    VDI's greater user flexibility and performance comes at a higher cost for servers and storage in the data center. Picking the right technology for the user requirements is essential to success both with the end user and in the data center. Most likely, IT will use a combination of all these technologies in order to have a balanced desktop and application delivery capability while also meeting capex and opex requirements.

  • Power and cooling
    In bringing these technologies into the data center, IT may have some unexpected results if the transition is not carefully planned.

    The first and most obvious result of moving the desktop computing and storage infrastructure into the data center using VMware's VDI or Citrix XenDesktop is that it adds more servers and storage to the data center. On one hand, this move better secures both the desktop compute and data resources. On the other hand, it requires more power, cooling and space -- often a commodity in data centers -- for the virtual desktop hosts.

    Even when desktop application distribution using streaming and virtualization technologies is based in the data center, servers to build and stream the applications and accompanying storage to hold the images being streamed will require additional power, cooling and space. When a data center is struggling to keep up with the business server demands for these three commodities, be sure to take a very close look at the total costs versus the benefits of moving desktops into the data center.

  • Network load
    The network is another area that these technologies will put additional strain on. Often, it's assumed that because networks have become so stable, this additional load should not cause problems. Well, tell that to the network admin who just spent the night working on a switch failure. Yes, networks have become significantly more stable over the past 20 years; however, these technologies rely heavily on the network and may take down a poorly designed or already stressed network.

  • Organizational structure
    Organizational issues are another possible side effect of moving desktops into the data center that should be considered and addressed up-front. Typically, in larger companies, the organization responsible for the data center, the organization responsible for the network and the organization responsible for the desktops are different and often have different work styles and expectations that may clash. To avoid issues, companies have been successful in creating cross-functional teams to work through both the technical and organizational challenges prior to the move so that everyone is on the same page from the start.

  • User and application mismatch
    Additionally, there are both users and applications that don't fit with the virtual desktop scenario, at least not with the technology as it stands today. One example of an application mismatch is CAD/CAE and other design and engineering applications with very stringent graphics requirements. In this case, IT can use PC or Workstation Blades with either hardware or software-based graphics acceleration, such as Teradici Corp.'s PC-over-IP hardware-based solution or Hewlett-Packard Co.'s RGS (Remote Graphics Software) software-based solution. This allows IT to centralize the compute engine and storage in the data center while providing the user and applications with the graphics performance needed to do the job.

    A common user mismatch, with IT centrally controlling desktops and applications, is in a development lab where the engineers must have complete control of the desktop environment for development and test purposes. That is not to say desktop virtualization wouldn't be appropriate in this case. In fact, desktop and/or application virtualization technologies can significantly reduce the time it takes to reprovision a specific environment and is often used in dev/test for that reason. The difference is that the engineers would control the environment, not centralized IT.

    For most virtual desktops and/or applications, the good news about the user/application mismatch is that all the lead vendors and many new vendors are continually working on ways to reduce the barriers to having nearly all desktops centrally located in the data center. Examples of this include Microsoft's addition of Virtual Channel Extensions to RDP 6.0, which enables local device connections for remote compute sessions, either hosted or virtual. Another is Citrix SpeedScreen, which improves remote ICA users' graphics and video experience.

However, businesses -- and specifically IT -- will continue to wrestle with network, power, cooling and space challenges associated with placing more servers into the data center, whether they are running server applications or virtual desktops.

Anne Skamarock, director of research at Focus Consulting (, has been involved with computers and associated technology for nearly 30 years. She started her career as a software engineer developing custom scientific codes and as a Unix systems administrator. She moved to the systems vendor side and worked as a software engineer and in technical sales, marketing and management for both large and start-up systems and storage companies, including SRI International, Sun Microsystems and StorageTek. For the past seven years, Anne has worked as a market analyst focusing on the convergence points around systems, storage and software. Skamarock writes extensively for TechTarget's,, and others. She co-authored Blades and Virtualization: Transforming Enterprise Computing While Cutting Costs (Wiley). FOCUS recently finished a FOCUS Landscape Series on Desktop and Applications Delivery Alternatives.


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