I've received a couple of calls from some customers and partners that asked the same following question:

"What is the difference between Application Streaming to XenApp Servers versus Streaming an Operating System?"

The questions continued to come up even in the "Microsoft and Citrix: Better Together Tour" event that I spoke at this Monday at the new Microsoft Office at the Westfield Centre in San Francisco. Therefore, I've decided this would be an excellent first blog. Please allow me to give this a shot at blogging the explanation.

Application Streaming to XenApp Servers (Background):

For those of you that were previously unaware, the artist formerly known as "Citrix Presentation Server" is now called, "Citrix XenApp". In XenApp 4.5, the product has the ability to provide for Server Side Virtualization and Client Side Virtualization. Traditionally, previous versions of CPS/XA were dependant on the network to provide published applications. However, enter in from stage right our new buddy "Application Streaming". Application Streaming allows for you as a customer to install an application into an Isolated Environment. This isolated environment can be compared to a bubble. This bubble contains for all intents and purposes, everything that an application would require to run. This bubble is an island until itself, only to run within the bubble and therefore seperate or isolated from installed applications that are already installed normally on the CPS/XA server.

Imagine if you will, the possiblity to provide applications On-Demand to both XenApp servers and also to client endpoints (Laptops and Desktops). Therefore, these isolated bubbles are stored on a central file repository, NAS or otherwise, ready and ripe for delivery by stream. For example, if I install Microsoft Word 2003 in one isolated environment and Microsoft Word 2007 in another isolated environment, neither applications know about each other because they are in their own bubbles. Now, take it a step further and imagine where you have a sample of 5 XenApp servers that don't have applications installed on them. This is because the applications in their bubbles will be streamed on-demand over to the XenApp server at point of use. So, what does this mean for you as an administrator? Well, really a couple of things. Here is the net-net of it:

1. Centralized code base for apps to be delivered by stream.
2. The ability to bring up a CPS/XA server faster without the pain of having to install the applications.
3. The ability change an application during the production day (Although, this is between you and your maintenance cycle...) and apply patches and revisions as need be.

This is one type of application streaming. That streaming is to XenApp servers. However, you can also stream the same applications over to endpoints as I stated earlier...and therefore providing a delivery mechanism for applications that need to run on the user's physical machine and allowing them to detach from the network.

For a Flash Demo of Application Streaming, please point your browser to:

http://www.citrix.com/site/resources/dynamic/additional/demos/as/as_master.html

Please excuse the demo goober during the start of the video. Now that you have an background on Application Streaming to XenApp Servers, now we can begin to explain streaming an operating system.

Streaming an Operating System with Citrix Provisioning Server (Background):

Streaming an operating system to bare metal can be accomplished by using a seperate product called "Citrix Provisioning Server". The 10k foot view is that you are able to provision operating systems based upon workload types. For instance here is a great example, say that your company is at the end of their quarter. Heads are flying, paperwork is spinning and data is being entered into applications that could be fully consuming your server's resources. Well, it isn't practical today to add a server into the mix because of the sheer time it takes to build the server and then load the applications to eventually configure that application. It is pretty time consuming. Enter in our friend, Citrix Provisioning Server. With Provisioning Server you are able to boot a new server in PXE (Preboot Execution Environment) mode, get a DHCP address and have a server OS streamed to your bare metal machine in a matter of a reboot. Therefore, you are adding another server to be used for end of quarter work...and you did it with a few clicks and a reboot.

Using that same example, now jump with me to the future where end of quarter is far from your mind. With a few more clicks and a reboot of all of those servers that were being used for quarter end, you can re-provision those servers to become web servers, applications servers or rather anything that you'd like them to be. The concept here is that a virtual disk runs on a storage device and Provisioning Server then provisions that vdisk to a server or servers identified by their MAC addresses. It's actually really cool stuff and makes delivery of servers for new or previous workloads literally a cinch. One of my customers compared the product to "Multiple Personality Disorder/Reorder for Servers". I received a bit of a chuckle when hearing that. This technology will also be highlighted and utilized heavily in the upcoming release of our new product, Citrix XenDesktop. There are many blogs on Community.Citrix.com that you can spend a great deal of time learning about new technology.

Seeing is believing and I understand that there are those that need to assess the logical and hold the tangible. Originally, we purchased a company formerly called "Ardence" that allowed us to acquire this technology. I suggest that you watch both of these videos below to see Provisioning Server in action.

Citrix Provisioning Server Demo by Pete Downing and Mark Templeton:
http://mfile.akamai.com/8296/wmv/citrix.download.akamai.com/8296/iForum07/Demos/ProvisioningServerDemo.asx

Also, Provisioning Desktop Operating Systems:
http://www.youtube.com/watch?v=moIuHqIc-PQ

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I hope that this has provided a good explanation of the difference between Streaming Applications and Streaming Servers. Should you have any questions, please email me.

Thanks! - Jon