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When most people think of virtualization, they think of servers and products that let multiple server operating systems run on a single hardware device. Desktop virtualization extends this concept to the workstation, with multiple users connecting to a single terminal server which runs and displays their desktop. Because this desktop is usually just a depiction of a shared screen, the user experience is not as rich as on a local workstation. That’s why this technology has only been deployed in specific situations, such as companies that have made the jump to thin clients or for remote users who need a virtual workstation back at the data center.
While Citrix has always been known for its desktop virtualization, the application virtualization (first introduced in Presentation Server 4.5) is much improved. Application virtualization, which streams applications to workstations, is poised to become an integral part of IT strategy, and XenApp is well positioned to lead the charge.
Like its predecessors, XenApp 5 utilizes Citrix’s Independent Computing Architecture (ICA) protocol for client-server communication. While there have been improvements in competing protocols (Microsoft’s terminal server’s Remote Desktop Protocol comes to mind), ICA still clearly leads the pack. For end users, this translates into a smoother experience when using XenApp 5 applications or a remote desktop.
XenApp 5 application virtualization bridges the gap to the local workstation. Users still have a fully functional PC at their desktop, but applications are streamed to this desktop and run locally. In fact, the user usually cannot tell which applications are being streamed and which are installed locally. Common applications such as Microsoft Office 2007, Mozilla Firefox and Adobe Acrobat Reader — and even custom applications — can be delivered through XenApp 5.
Printing has long been the Achilles’ heel of desktop virtualization products, and any Citrix administrator will tell you it’s the number-one user complaint. In XenApp 5, there have been noticeable improvements. XenApp 5 includes support for XML-based XPS print devices, as well as a universal print driver that supports nearly all network and USB print devices.
The web interface to Citrix XenApp 5 is also much improved. The new sleek, black look modernizes the “blocky” application visualization from Presentation Server. After authenticating, the user sees a web page with tabs for applications, messages and settings, allowing for easy access to these areas. There are several new options to customize the layout of the web pages for pre-logon, logon, applications and messages.
Maintaining applications — patching, improving, upgrading — is one of the most time-consuming functions of most IT operations. Multiply the number of applications by the number of desktops in an organization, and you find yourself with quite a collection of problems just waiting to happen.
Citrix XenApp 5 offers the dream of configuring an application, installing and testing it — just once. Need to patch Microsoft Office? Patch it once on the XenApp server and the updates are automatically streamed the next time each user opens the application. No more patching every workstation. XenApp 5 is even smart enough to push just the new bits, not all the bits.
Another important component of XenApp 5 is Linked Profiles. In previous versions, Citrix administrators put together a “profile,” which usually mapped to a particular kind of business user. This profile included all the applications that user would need to do his or her job. Of course, there are many different types of business users, so a typical Citrix farm deployment might include six to 12 different profiles, or more. A problem arises when one application that is used in a number of the profiles needs an update: The administrator has to rebuild each profile. With Linked Profiles, however, each profile still consists of a number of applications, but instead of being compiled as part of the profile, the profile simply links to each individual application. Therefore, the application is installed (and subsequently upgraded) only once, even though multiple profiles might use the application.
Application load balancing and prioritization have also been improved. Administrators can now prioritize users or applications. This insures that critical sessions or applications always get the lion’s share of processing power. First, the administrator assigns a priority level (1 equals low priority, 2 equals medium, 3 equals high) to each user and each application deployed. Then, each user receives a share of the CPU allocation based on a resource allotment calculation of an application in that user’s session.
For example, consider two users on a XenApp 5 server. User A has a priority level of 1 but is using a critical application with a priority level of 3, so his resource allotment is 1 x 3 = 3. User B has a priority level of 2 and is using a medium-level application, so her resource allotment is 2 x 2 = 4. Hence User B receives four-sevenths of the XenApp server’s resources, while User A receives three-sevenths.
Session-level application and system performance monitoring for Citrix XenApp infrastructures delivers real-time performance visibility for proactive problem solving and infrastructure optimization. EdgeSight monitors the Citrix farm’s CPU, memory and input/output; it also features full ICA protocol monitoring and synthetic session performance analysis. This lets an administrator measure the performance of the environment by regularly and automatically mimicking a user’s typical tasks and recording the response times.
How does all that streaming affect network performance? For a gigabit LAN connection, it’s not an issue. But what about the branch deployments, which may stream over a T1 or less robust line? XenApp 5 has been integrated with another product, the Citrix Branch Repeater, which accelerates the streaming to remote locations. This should improve the startup and response of applications at a remote office. However, network utilization and performance across a WLAN will always be a concern and remains a challenge for manufacturers.
Citrix XenApp 5 was built for Windows 2008 Server. While in the future this will be one of its strengths, many organizations have not made the leap to Microsoft’s new server operating system. However, XenApp 5 does run on Windows 2003 Server, and mixed farms are allowed. This should let companies migrate at their own pace.
Even with the promises of cost savings in application maintenance, virtualization technology itself requires its own care and maintenance. There are cases in which it is clear that application and desktop virtualization greatly benefit the IT department and its users; but there are also cases in which the cost/benefit analysis is not so clear. As with any new technology, if you’re thinking of taking the plunge, make sure you test the water and keep your eyes wide open.
Dr. Jeffrey Sheen is the lead enterprise analyst for Grange Mutual Casualty Group of Columbus, Ohio.