Thin client computing done right with Citrix XenApp

Deployed correctly, Citrix XenApp can deliver on the remote desktop promise.

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Few IT duties are as universal as the care and feeding of the corporate desktop. While other aspects of IT get easier thanks to new technologies like server virtualisation, there's still no magic pill to alleviate the day-to-day drudgery of maintaining and securing hundreds, thousands, or tens of thousands of desktop systems.

The drawbacks of desktops go beyond the burdens of management and maintenance. They involve employee mobility, client hardware refreshes, data security and under certain conditions, even power consumption and cooling.

One answer to desktop sprawl is thin client computing, which consolidates user applications and environments at the server, vastly reducing the overhead associated with desktop software and hardware. Users access the host server over the network using a variety of clients, such as low-cost terminals or aging systems that would otherwise be obsolete. Instead of running around babysitting desktops, administrators take care of business in the data centre, saving time and resources.

Unfortunately, there's no straight-and-narrow path for migrating from fat desktop clients to thin clients. But there are more options than ever before.

Server-based, thin client computing today takes several forms. Traditionally, thin client solutions revolved around groups of terminal servers running dozens of individual user sessions. The back-end frameworks were comprised of Microsoft Terminal Services (renamed Remote Desktop Services with the arrival of Windows Server 2008) and occasionally a Citrix infrastructure to improve performance and manageability. In recent years, VDI (virtual desktop infrastructure) has emerged to offer a different approach, using virtualisation to split out each user session into a VM (virtual machine) unto itself. Like traditional thin client solutions, VDI uses the Terminal Services/Citrix connection broker model to deliver the virtual desktops to users.

Traditional thin client computing

Terminal Services (aka Remote Desktop Services) is the low-hanging fruit on the thin client tree. It's extremely simple to buy a few cheap thin client devices, install Microsoft Windows Server 2003 or 2008 on a server, configure the Terminal Services or Remote Desktop Services role, and have the clients connect to that server for their desktop sessions. For certain use cases, such as data entry, forms processing, call centre duty and hospital rounds, Terminal Services may be all that's necessary.

Generally speaking, this solution is best suited for single application or light applications use, as the complexity and overhead associated with more applications and more users can quickly overcome the lower relative cost. There can also be issues with user acceptance and overall interaction with traditional thin client computing. Users accustomed to music and movies on the PC may be dismayed to find that audio and video playback is spotty at best, or plain absent. The use of USB peripherals can be extremely problematic, and printing across slower WAN links can result in sluggish user sessions.

The benefits of Terminal Services are low price and ease of installation and maintenance. The downsides are a lack of scalability, potentially problematic performance over lower-bandwidth and higher-latency connections and overall manageability. In short, it'll do for a small, dedicated rollout, but once it escapes those confines, it's generally time to move up the chain.

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