Citrix XenDesktop and Citrix XenApp now offer customers two different computing models for centralizing their client computing. I have had about a dozen or so customer conversations regarding where the best use of each technology is. I want to share that with everyone.

People ask me whether the IT and business problems to centralize have changed. The answer is – they have not. Costs, compliance/security and flexibility for access remain to be IT challenges that centralization can solve. If you think about the culprit that keeps the TCO of desktops high, it is application deployment and management.

The two problems that customers have been able to successfully address with XenApp are:

1. Delivering appa to users anywhere – typically customers start with virtualizing problem apps and grow their XenApp usage overtime.
2. Virtualizing the full desktop with all the apps – it has worked great for task based workers who use standardized locked down environments with few apps.

Overtime, XenApp has addressed several key challenges in addressing those requirements including scalability (via 64-bit), app compatibility (via app isolation environments any app can be made compatible with XenApp), graphics (via SpeedScreen), performance monitoring (via EdgeSight) and offline support (via portable app virtualization/streaming). This has enabled an even broader use of XenApp for virtualizing more apps within existing XenApp customer base.

Now, XenDesktop enables our customers to expand desktop virtualization to not just task workers (served via XenApp shared desktops) but also office workers (VM/Blade based dedicated desktop). However, dedicated desktops always come at a cost. The cost is reflected in the user density per server. Where as a dual core XenApp server can serve 100 shared desktops, XenDesktop can serve about 10-12 users per dual core server. So, the cost of hardware required per user goes up from $25-$50 for XenApp to about $250-$350 per user on XenDesktop. Hence, the XenApp based shared desktops will always be the most cost effective way to deliver virtual desktops.

Both models have their merits and limitations. As stated XenApp serves desktops in the most cost effective manner and is best suitable for task based workers. The limitation for XenApp is around personalization capabilities – end users cannot fully personalize their environment, which is a need for mainstream office users. XenDesktop, on the other hand, is best suited for virtual desktop delivery for mainstream office worker. The real limitation lies in offline access requirements, or advanced peripheral support.

LAST BUT NOT THE LEAST – delivering applications using XenApp radically lowers TCO of BOTH physical and virtual desktops by enabling IT to centralize the apps and never install them with the desktop. There are different benefits for physical PCs and virtual desktops.

With physical PCs, benefits of using XenApp are:

1. Increases the life of PCs
2. Enhances application and data security
3. Enables app delivery anywhere using any device
4. Lowers the cost of application management

With XenDesktop (virtual desktops), benefits of using XenApp are:

1. Dynamic provisioning of virtual desktop implies that a user’s desktop always stays pristine with no apps installed – all apps are delivered (using streaming or hosting technologies) enabling an on demand assembly of personalized desktop at the time when a user logs on.
2. Predictability and Capacity planning on VDI – Separating all LOB apps that have unpredictable (problematic) resource requirements, and running them on separate XenApp servers, prevents over-provisioning the VDI server architecture and can reduce the number of servers required for virtual desktops, improving the TCO of virtual desktops.
3. Application and license management – each app can be controlled granularly. You have complete visibility into who has access to the applications and who accessed which application when.

In summary, IT now has two excellent options (XenApp and XenDesktop) for building their virtualization infrastructure to meet the needs across all their use cases:

Task workers – use thin clients with shared desktops delivered via XenApp
Mainstream office workers – use desktop appliances with dedicated desktops delivered via XenDesktop
Mobile users – use XenApp to deliver all streamed or hosted apps for both connected and offline access

At Synergy (http://www.citrix.com/synergy), this topic will be discussed at length. Come visit us!