I am sure by now you have heard about this great new way of virtualizing applications with XenApp called VM Hosted Apps – now in Feature Pack 2.  We have been talking it up  everywhere  from Citrix sponsored events, such as Synergy, to blog postings, to webinars, etc.  The feature allows you to deliver applications to end-users from a virtual workstation.  The traditional method of delivering  applications with XenApp  is to install or stream the application to the server or to the client device.  This new feature is by no means designed to replace this traditional method. As a matter of fact, we expect VM Hosted Apps to be far from mainstream. 

VM hosted apps isn’t one of those features that you simply spin up and see what happens.  First, it has totally different components than the typical XenApp customer is used to.  In this version, you’ll have a Desktop Delivery Controller(DDC) that uses a separate farm database and new MMC snap-in that is separate from the traditional XenApp infrastructure.  Your application is installed and delivered by a workstation that communicates with the DDC which is responsible for brokering connections to the virtual workstation.  It’s not hard but it certainly isn’t as simple as the rest of the XenApp infrastructure. That doesn’t change the fact that  VM Hosted Apps is a brilliant idea….  I want to encourage you to check it out and so to help make it easier, I’ve included a few helpful hints below.

To have an  efficient setup, you will need

  • Some type of server virtualization  infrastructure. You can pay for one from those _other_ guys or you can use XenServer which is free! Your choice but it’s a pretty obvious one.  That is,  unless you plan on purchasing extra cooling devices after placing numerous amounts of physical desktops in your data center (RE: Blade PC’s). 
  • You will need one workstation for each concurrent user. Once you decide where to  host the workstations, you will need to determine how you are going to get the workstation operating system  onto the physical or virtual machines.  It supports Windows XP, Windows Vista, and Windows 7. 

The best way to illustrate how important a decision this is, is with an example.   Lets say you are the administrator for a large company with thousands of end users.  The company wants to deliver a  highly  specialized application that is not Terminal Services compatible.  The application vendor only supports this app on Windows XP.  VM Hosted Apps is the feature for you only if  you are sure that the app won’t work on Terminal Services, or that Streaming the application is not appropriate either. 

Now that Citrix provides three methods of delivering applications, your  thought pattern should follow something like this.  

  • Can I install or stream the app to my XenApp Terminal Server?
  • Can I have it streamed to the client device? 

If the answer is “No” to both questions, then VM Hosted Apps is the logical choice.  Aside from the new skill sets that your Citrix Administrators  will need to attain to administer this appropriately i.e. XenDesktop, Provisioning services, XenServer, you need to consider the Microsoft aspect.  You will need to purchase Microsoft’s VECD licenses to license those virtual desktops.  One good thing about VECD licenses is that one  license is good for 1 physical device and connections to 4  windows virtual machines.  The bad news is, you must renew the licenses yearly.  So you will be paying  repeatedly unlike Terminal Services licenses where you pay just once.  

Once you know what you are getting into when using VM Hosted Apps, and you determine that this solution is right for you, here are some best practices that might help you stay out of the long dark rabbit hole that troubleshooting a bad setup can get you.  Make sure your DNS and Active Directory are flawless.  Virtual Desktops find and register with Desktop Delivery Controllers using something called a Service Connection Point (SCP).  SCPs are a feature of Active Directory and allow services to be published so that they are found by different components.  If you keep getting strange errors in your event viewer that relate to Active Directory, I highly suggest you  fix them before embarking  on a VM Hosted App  setup.  Use utilities like Active Directory Explorer to help you determine the state of  Active Directory.  The next culprit that could derail your setup is DNS.  Forward and reverse look up must be configured and working properly. 

Now lets  go back a bit.  One of your first decisions was how you were going to deliver  those 100 desktops/virtual machines to your end-users that needed to use that specialized application.  Will you build 100 desktops manually? Even though you can use private virtual machines for each user you should try to avoid it if you don’t need it.  Instead, the most efficient way to do this is with Provisioning services.  You will get Provisioning services for use with VM hosted apps in XenApp Enterprise Edition or higher. Use Provisioning services to create a virtual disk with the OS already installed and configured and then stream that OS from the centralized vdisk to create as many virtual workstations as you need.  It will even spin up these machines on demand. The downside is, if you don’t already know how to use PVS, this is yet another skill set that you will need to attain to support VM Hosted Apps.

As a readiness instructor, my job is to deliver the naked truth. While at times it may seem like I am describing  reasons not to  use this feature, this couldn’t  be further from the truth.  VM Hosted Apps is a powerful feature and if you already know how to setup XenDesktop and PVS, then this should be a breeze for you.  If not, learning how to set it up will give you the bonus of preparing you for the world of desktop virtualization in general so it is certainly not niche expertise. As homework (I am a teacher after all), go to to Citrix eDocs and do your homework before you do ANYTHING.  Then get on that white board and draw a design depicting where these new components that you just learned about are going to fit in your environment. Then get out your calculator, calculate your budget needs and get organized. Again great feature …but if you want to succeed you’ve got to do your homework! I am working on CitrixTV recordings to walk you through the setup so look out for that.

Since this feature has generated so much buzz, I just posted Part 2 to take you through the components and configuration.

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