We are always picking sides, our favorites! Today there is a growing debate on where application virtualizationshould be performed, 'client side' or 'server side'. The concept of separating the application from the underlining OS can be done on the client (Desktop/laptop) and on the server.

Many references to application virtualization (http://virtualfuture.info/2008/06/virtualfuture-appchart/) are usually about client side application virtualization. Products like SoftGrid, ThinApp, InstallFree and  XenApp application streaming (the application virtualization feature within XenApp) are mainly referring to the client side of virtualization. All these products do a great job of server side virtualization also.  In many XenApp installations customers are using server slide application virtualization to improve the return on their XenApp investment. From what I've seen there are more server side implementations of application virtualization, now the idea of client side application virtualization is getting into the spotlight.

There seems to be a debate brewing as to which is the best way to go - client side or server side? Do you run the traditional server based model of computing and delivery apps to users from the server or is it better to deliver  and run the apps as close as possible to the user on their PC? The good news is that application virtualization is applicable to both client and server side, so at the end of the day as long as you are looking at virtualization your applications you are heading in the right direction. Can you get the best of both world? The ideal scenario would be to prepare your applications for virtualization once and then decide later as to where would be the best place to execute the application, client side or server side. Even better would be a system that can decide based on policy, users connectivity or application usage controls where to vertualize, at the client or the server. The ultimate would be a system that can change where the application is virtualized and executed, based on the above scenarios - so in one instance you run your application on the client, and then, say, when you're, outside the corporate firewall, you would run the same application from the server. Of course you want to only use one instance of the virtualized application in both cases.

XenApp is an application delivery system that uses both client side and server side application virtualization to deliver applications in the most optimal way depending on policy. The application hub within XenApp stores the profiled applications and delivers the same application to the client or the server. Anytime the application is modified or needs to be updated, you only need to make the changes to the profile in the application hub and the virtualized application on the client and/or server is updated automatically. You can profile and store all your Windows applications in the application hub. Additionally XenApp works with Microsoft 'SoftGrid' application virtualization and other application virtualization technologies. XenApp is the overall delivery system for all windows applications. For example if you are using SoftGrid as your application virtualization technology that's fine, the XenApp delivery system still works in the exactly the same way, even more you can mix both SoftGrid and XenApp virtualized applications within the XenApp application delivery system. So if there is a specific feature within application virtualization you need, or you have already bought an application virtualization technology or you prefer a specific application virtualization vendor; you can use a specific application virtualization technology within the XenApp application delivery system.

The next version of XenApp which will also be on the Windows Server 2008 platform will provide even more features to enable application virtualization with XenApp. You should be using both sides of application virtualization; enabling all your Windows applications for all your users. You no longer need to decide which application virtualization side you are on, you can be on both sides, delivery the best of all worlds.

Are you working on both sides?

Application Virtualization is getting serious attention these days. Many organizations are considering the value of application virtualization as a fundamental part of their overall virtualization strategy. Take a look at the search traffic for the three major types of virtualization: server virtualization, application virtualization, and desktop virtualization. Search traffic for "server virtualization" is trending flat while "application virtualization" and "desktop virtualization" are increasing.

Many people interchange the terms application virtualization and application delivery . Both are important but they are not the same thing.

Application delivery is  about a bigger value proposition - it's about  getting applications to their users. User productivity is a key driver for application delivery. Ensuring applications are always available for these users to be as productive as possible. Improving the user experience is one of the main benefits of a good application delivery system. Application delivery is also about reducing the cost of getting applications to users and ensuring the most secure environment for applications and their associated data.

Application virtualization is a means to an end. Application virtualization is a technology by which application delivery can be improved. Application virtualization like any virtualization technology is about separating the target (the application) from its physical constraints (the operation system and its various components); separating an application from the confines that normally dictate the conditions of how and where the application executes.

A good application delivery system would take advantage of all possible application virtualization technologies to provide users the most flexibility, while considering costs and security. Application Delivery is about business value while Application virtualization is technology to deliver the business value .

For years Citrix XenApp (the new name of Presentation Server http://www.Citrix.com/XenApp) customers have been using XenApp, as an application delivery solution, each year, getting  more value as Citrix continually improves and adds more functionality as the needs of users increase. (To learn what Citrix is doing for the next release or XenApp, refer to project Delaware http://www.Citrix.com/Delaware). 

These customers understand the relationship between XenApp and Terminal Services and how together they provide a powerful solution. A question I often get asked is; do I see a day when the functionality of TS will be enough that the need for XenApp will be lessened? Some customers expect this is just a matter of time and assume one day Terminal Services will be enough. 

 The simple answer in my view is that TS will never be enough, because the good enough bar continues to move up.  The good enough bar is the level where a customer is comfortable with the functionality that they are prepared to accept that level of functionally, usability, security etc, is enough for their organization. 
To correctly answer the question you need to ask what is good enough? It is a different answer for different organizations. It's not just a matter of size or even complexity but it's about what dependency the organization is putting on the overall solution and how does an organization see this changing over time. 
Also if you asked what was good enough in 2003 and what is good enough today you will get a very different answer as organization's needs have changed in so many different ways.  

This change in what is good enough, the changing levels of the good enough bar, is due to a number of factors: 
IT has become more critical, and many would not survive today without their IT systems and for some, IT is extremely strategic and is a competitive weapon.  
IT has also become much more complex, with all business processes now automated and each linked in some way. Security issues have also raised the good enough bar, organization are looking for the most secure way to provide application access to users. 
Users needs have also become more complex, using many more applications; they are much more demanding, expecting to have access to their systems all the time.   

Applications themselves are also more complex, and there are multiple generations of application types with organizations. 
I'm sure there are a number of other factors you could add that continue to drive the good enough bar upwards. 
Finally this is not a static environment, the good enough bar of tomorrow will be much higher than today. 

Understanding  that the good enough bar is always changing you can understand why I would say that TS is not good enough even with the new features of Terminal Services in Windows Server 2008 ( http://www.Microsoft.com/WindowsServer2008 ), because organizations are not prepared to take a risk and deploy a system that could be otherwise improved by adding more value. 
Citrix XenApp uses the Terminal Services platform to provide the most complete application delivery solution with the best, centralized control, application compatibility, optimized user experience, comprehensive access and scalability. 

As more customers realize the enormous benefits of this new model of computing; delivery all applications anywhere to their users; they will want the best possible solution, one that has the most complete set of features. A solution that has the best chance of being successful today and also adapt to their future needs. Whether an organization is deploying a few application or all their applications, they should look at the most complete solution knowing they will end up with the best end result. 

Then there is the question of cost. What customers have found is it takes less time and resources to deliver a solution that is more complete, that works as a complete system, than try to piece bits together, this weighed with the risk factors shows it's always better to start with the most complete solution the 1^st time rather than add functionality later. There are too many other things that need to get done, why take the risk?  
Organizations that have been using XenApp for more than 6 years know this question has come up each time Microsoft releases a new version of Windows Server with added Terminal Services functionality. To date this has been with Windows NT 4.0, Windows 2000 Server, Windows Server 2003, and now with the new Windows Server 2008. So for all of theses and for the next release of Windows Server the answer is 'no' TS is not good enough because the good enough bar continues to move up! 

To understand more about XenApp and Terminal Services, I would refer you to another blog by Bryon Thomas on Terminal Services and XenApp, Bryon lists a number of tools available that list the enhanced value of XenApp and he is asking for suggestions on what other tools are needed. ( http://community.citrix.com/blogs/citrite/bryont ) 

I welcome your comments and views on the concept of the good enough bar, how is it rising in your organization?  

Nabeel Youakim

VP & Product Line Executive,

Applications Virtualization Group, Citrix Systems