There is no lack of evidence of the pain of provisioning, maintaining, and using traditional PC desktops. User satisfaction is low; maintenance costs high; and stories of lost data, hacked networks, and virus, worm, and DoS attacks are reported almost daily in the press. As Credit Suisse noted recently in a report on Desktop Virtualization, “What began as a useful tool that boosted productivity has grown into a bloated device requiring constant upgrades and maintenance due to compatibility issues associated with patches, new hardware, and software releases.”

Many IT departments are considering using virtual desktop infrastructure (VDI) to centralize and virtualize user desktops in a secure location, leveraging secure data centers and putting the desktop close to support staff. What about performance, cost, and customization? Current deployments of centralized desktops have effectively delivered the centralization part but for the most part have been a shared resource, affording very little in customization and little general applicability to multimedia or graphics-rich applications.

The virtual machine approach delivers a fully malleable PC environment since it is essentially a complete desktop PC stored on a server in a data center (see Figure 1). Only within the past year or two have client communications protocols developed the level of performance to deliver VM-based desktops satisfactorily. These protocols eliminate any user perception of latency and slow screen refresh to deliver traditional PC-like graphics performance over all but the slowest of corporate WANs.

What about cost and complexity? You might expect that replacing a lot of PCs with centralized CPUs and multi-terabytes of disk storage to keep the personalized OS and applications is going to be extremely expensive. Given the availability of fast, multi-core, multiprocessor 64-bit servers, dozens of desktop sessions can be very efficiently hosted on a single machine. However, the storage scenario is the harder nut to crack. Keeping full OS images in the data center to load into each virtual machine is hugely wasteful and very difficult to manage. The use of image cloning (starting from a single OS image and delivering copies to the virtual machines) can save storage space but as soon as the original OS image needs to get patched, all persistence is lost and the clones must be regenerated and distributed. To address all this, two best practices come to the rescue.

The first is separating the OS from the apps via application virtualization (see Figure 2). This kind of technology can deliver a lot more applications and can be tuned to deliver them directly to a virtual desktop. This means a best-performing application can be delivered to a best-performing unencumbered desktop OS without storing the application on the virtual machine. These can be presented to the user’s VM via the client communications protocol or streamed to the desktop virtual RAM via client-side virtualization, allowing the user access to an application offline. In either case, only one copy of the application needs to be stored and maintained. This copy can be streamed or presented to thousands of users on demand. Note that this does not change licensing terms for most applications.

The second best practice is to maintain a single, clean, updated OS image for all desktop clients (see Figure 3). OS streaming or virtual OS provisioning eliminates storage and support issues by doing away with the need to keep one OS image for each Virtual Desktop. Instead, one optimized, corporate-standard Windows XP or Vista image is maintained on the network. All the virtual machines PXE boot this same image over the network and user-specific configuration/profiles are applied at logon. Because all images are delivered by reference via streaming, users always run the latest patched OS version. You no longer need to patch or change virus definitions for 100, 1,000, or 10,000 desktops. It can now be done once on the golden OS image and is delivered to each user the next time they log on.

A new way of delivering desktops to your users demands new ways of managing these desktops for your organization. Simply migrating desktops to a centralized location adds just about as many problems as it solves. Deploying a separate application delivery infrastructure and provisioning a single OS image are two best practices that can go a long way towards making VDI a reality.