For those of you who attended the 1,000 XenDesktop Users in 90 Days TechTalk on December 8th, I’ve gone ahead and compiled the questions and provided you with answers.  If you missed the TechTalk, you can see it on CitrixTV

Q: Would the “ideal” solution be to run every app on XenApp instead of installing on XD?

A: There really is no “ideal” solution because every application is different.  You need to look the application characteristics to determine how it will impact your environment. Putting large line-of-business applications in a virtual desktop typically kills the hypervisor scalability due to RAM requirements but placing these applications on XenApp offsets this.  Other applications place on XenApp will work but will not allow the user to have complete control of the application interface customization, which makes it a good candidate for the virtual desktop. Also, you can install the applications into the virtual desktop image, although every user who uses this image will see the applications. So installing the applications into the image might require the creation/management of multiple desktop images. There is no good answer, just guidelines based on the application type (Base, Anomalous, Resource Intensive, and Technical Challenging). 

Q: Can the webservers, XenDesktop controllers, XenApp servers, and Provisioning server be VMs in the hypervisor cluster/pool

A: Every component can be virtualized and it is supported. Different hypervisors will give you difference performances over other components, but each hypervisor is going to add a level of overhead.  You also want to look at the component-level utilization to get the most mileage from your physical servers. For example, Provisioning services is going to impact your network link while the XenDesktop controllers will consume CPU.  Ideally, you want to try and balance out these components so that the components of the physical server are maximized without impacting overall usability.

Q: Why are you recommending creating multiple farms while scaling out rather than adding additional DDCs to the existing farm?

A: It is based on the underlying XenDesktop architecture.  There is no technical limit to the size of a XenDesktop farm, but when you get to a certain size and your bootup and logon storms are so intense, you will start to see logon times slowing down as these requests go through the master controller.  You have 2 options:

  1. Add more processing power to the master
  2. Add a new master, which equates to a new farm

On the surface, people often think a single farm is the best approach but if you redline your components, strange things can happen (not only with XenDesktop but just about any software).  If you create building blocks, you are better able to expand the environment without a complete rebuild of a component because you have spare capacity and processes in place to simplify management of multiple blocks.

Q: Do you have any suggestions for network connection speeds on the Provisioning and Hypervisor system

A: Don’t use anything slower than 1Gbps. In fact, there are some people who are using 10GigE.  Basically it comes down to this, the faster the network connection, the more target devices you can support from a single Provisioning services server.  If you are using Windows 7, you can assume that to boot up the target device will take 200MB of network traffic.  Calculate this out fot he size of the environment you are trying to support. This will help you identify your network requirements.

Q: Does streaming apps add a significant amount of complexity, compared to running apps in XenApp or on the XenDesktop?

A: It is a different approach towards delivering applications into your virtual desktop, thus giving you another method to support.  If you already have a mature XenApp environment with hosted applications, keep using it.  If you don’t have a mature XenApp, look at installing your base/common applications into your virtual desktops. You will reach a point where you start to increase the number of desktop images. At this point streaming might be a more optimal solution to help reduce the number of desktop images you need to support. This is a decision that is made during the analysis/design phase. 

Q: The more desktop images.. the more disk storage in the data center needed correct. So would the preferred method (if possible) have fewer images?

A: Yes. Although 1 desktop image can be used by thousands of users.  Each image is only as big as you make it (15GB for XP and maybe 30GB for Windows 7).  So if you have Windows 7 images that is only 150GB, not huge.  However, the bigger benefit of reducing the number of desktop images is in managing them.  Instead of patching/updating 5 images, you only have to do 1. 

Q: When using XenDesktop with XenApp, does the user have two profiles or are the profiles somehow “shared” between XenApp & XenDesktop?

A: Two different ones.  You can use tools like the Citrix User Profile Management solution or third party tools like AppSense to integrate the profiles into a single container for multiple operating systems. Your question does bring up a good point, you cannot forget about the profile and the implications on the system.  

Q: Can the License Server be made redundant?

A: Yes. However, if the license server is offline, users have a grace period where they can continue to connection and work. If you virtualize the license server, you can easily move the virtual machine from one physical server to another with XenMotion.  This will not impact the users.   Probably the cheapest and easiest approach to take.

Q: we have an existing XenApp farm, and we are looking for a good White Paper on how to set up a new XenDesktop Test farm with our existing and how to go about it (integrating with Licensing server, etc). Is there a good paper you can recommend? Thanks

A: Yes, take a look at the following.

Also, take a look at this site for other white papers on XenDesktop that might be helpful for you.

Q: Is a 3rd party application necessary to make the Provisioning servers completely High Available without sessions being lost?
A: No.  When you turn on the High-Availability feature with Provisioning Services, you are all done. If one server fails, the target devices receiving their stream from the failed server will reacquire the stream from another server in the HA set.  The user might notice a pause in the system while the stream is reacquired and synchronized, but the user will not lose their work.


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