I am a big fan of virtual desktop infrastructure (VDI), which is the name often used when talking about recentralizing...
desktop computing back in the data center using server virtualization technologies as the underpinnings. VDI has the potential to significantly increase desktop data security, reduce desktop service calls and costs associated with tech refreshes and desktop and application management as well as power and cooling throughout the company. However, they don't call it Virtual Desktop Infrastructure for nothing!
Sure, you gain all those things, but it's important to understand that moving desktops into the data center has the likelihood of taxing every aspect of the IT infrastructure if you bypass appropriate up-front planning. There are three areas I recommend companies consider or inspect before launching a VDI deployment: current network bandwidth/stability, desktop storage requirements and application management procedures. These three considerations often require creating a cross-functional team, especially in larger companies, to discuss, plan and validate readiness to proceed.
The network and VDI
VDI, regardless of whose technology is used, relies heavily on the network. The desktops running in virtual machines on a server collect graphical information and send it across the network using a protocol such as RDP, ICA or one of the other protocols/methods for remoting graphical content on the user's display (which protocol to use is a whole other discussion). If the network is already reaching bandwidth limitations, then adding more traffic (especially traffic over the WAN) is likely to bring the network to its knees -- even with using very efficient protocols.
Another network aspect to think about is network design. Consider this: If there is a failure, how well does the traffic route around the failure? The last thing any call center wants is to have hundreds of angry users calling because they can't gain access to their work. The good news is that tools to model network bandwidth and routing have been available for years.
Storage and VDI
When IT organizations decide to move to VDI, they begin by building out the associated storage infrastructure. There are two aspects of storage that surprise them at this point: costs and right sizing.
Let's address costs first. Today, most desktops come with an inexpensive 80 GB hard drive, standard. Now you are going to take the data off the inexpensive hard drive and store it on an expensive SAN or NAS device in the data center. Of course, SAN or NAS storage isn't "required" to implement VDI -- only if you want to also have all the advanced management capabilities that rely on live migration of virtual machines such as dynamic resource management. Companies have reduced some of the costs by implementing an iSCSI SAN storage infrastructure for the VDI.
The second storage surprise is having to decide how much storage is required per desktop. Often IT will over-provision storage for each user. With 80 GB provisioned per user for 100 users, IT must now support 8 TB of SAN or NAS storage in the data center. Fortunately, there are a few ways around the storage provisioning conundrum. One of them is to use thin provisioning technology, such as Dell's EqualLogic or 3PAR's Thin Provisioning. This technology allows IT to over-allocate physical SAN capacity, which provides better storage utilization and lowers storage costs. Another solution is to reclaim storage that was over-allocated. Vizioncore Inc.'s vOptimizer Pro is an example of a software solution that provides automated storage reclamation.
Applications and VDI
VDI eases desktop management, but a desktop is not simply a compute engine and an operating system. Each desktop requires a suite of applications that a user needs to perform his or her job. Unless IT designs an application management process for the VDI implementation from the start, much of the promised value of VDI will be lost. IT will spend hours spinning their wheels on updating and managing application images for each virtual desktop deployed.
My recommendation is to strip the OS image of all but essential applications (often tied to the OS), such as Internet browsers, and deploy all other applications using application virtualization. Application virtualization allows IT to create, update and manage one image of the app. Each virtual desktop would access the single image of the app without actually installing it within the desktop space. This has the added benefit of reducing the storage footprint for each desktop. Some examples of application virtualization include Citrix XenApp, Microsoft App-V, VMware ThinApp, and Symantec Altiris and AppStream.
Implementing a virtual desktop infrastructure cannot be performed in a vacuum, especially in companies where different organizations have "ownership" of the components within the IT infrastructure -- such as networking, storage, and application support. Even for medium-sized companies that have three people to support hundreds of desktops, it's essential to understand how VDI can and will affect the existing infrastructure and processes.
About the Author: Anne Skamarock, Director of Research at Focus Consulting, has been involved with computers and associated technology for nearly 30 years. She started out as a software engineer developing custom scientific codes and as a Unix systems administrator. She moved to the systems vendor side, working as a software engineer and in technical sales, marketing and management for large and start-up systems and storage companies such as SRI International, Sun Microsystems, and StorageTek. For the past seven years, Anne has worked as a market analyst focusing on convergence points in systems. Anne writes regularly for TechTarget's SearchEnterpriseDesktop.com, SearchStorageChannel.com and SearchServerVirtualization.com and for business and technical white papers. Focus has recently finished a FOCUS Landscape Series on Desktop and Applications Delivery Alternatives. She co-authored the book Blades and Virtualization: Transforming Enterprise Computing While Cutting Costs (Wiley).