Windows desktop upgrades are a bit of a problem for IT pros, to say the least. The new features in Windows 7 are desirable, but the application-testing process can be extremely time-consuming and expensive. Thankfully, Microsoft offers two tools that are designed to make the desktop OS upgrade process much easier -- App-V and Med-V -- and
App-V and Med-V are both available to Software Assurance customers via Microsoft Desktop Optimization Pack (MDOP). The two tools take very different approaches to the application virtualization process, and although these approaches seem contradictory at first, they can complement each other.
Here are basic descriptions of each tool and why running App-V in a Med-V environment can make moving to the latest version of Windows a bit easier.
App-V allows applications to be packaged along with all of their dependencies so that the apps can be streamed from servers to end users' desktops. This frees administrators from having to install apps directly onto user desktops and maintaining multiple desktop images and the programs that individual users require. Instead, IT professionals can maintain a single standardized desktop image that lives in the data center and then stream applications to users on an as-needed basis.
Ironically enough, one of the big selling points for Windows 7 is Windows XP Mode -- a fully functioning, licensed copy of Windows XP that runs within a virtual machine (VM) on Windows 7.
What makes Windows XP Mode different from other VMs is that applications running in XP Mode are seamlessly available through the Windows 7 desktop. Users might not even realize that such apps are actually running on Windows XP.
Med-V takes this same concept and extends it so that applications can run within either Windows XP Professional (Service Pack 2 or higher) or Windows 2000 Professional (SP4). Whereas App-V packages an application with some OS components such as registry entries, Med-V creates a package containing the app itself and a full instance of Windows. By doing so, Med-V is able to eliminate any incompatibilities that may exist between an operating system and an application.
Running App-V in a Med-V 2.0 environment
By this point, you might be wondering why you might want to use App-V and Med-V together.
Well, App-V is great for application management and for allowing otherwise incompatible apps to coexist, but it does have at least one major limitation. Before an application can be used with App-V, it must be sequenced and packaged. The sequencing process is OS-dependent. When you sequence the app, you actually have to install it so that the App-V Sequencer can monitor the changes that the program makes to the operating system. If you have legacy applications that cannot be installed to a supported OS -- Windows XP, Vista, or 7 -- then the app cannot be sequenced for use with App-V.
So why not just run all of your applications with Med-V? The biggest barrier to running apps this way is performance. Remember that Med-V packages apps with a full-blown Windows operating system, whereas App-V packages only what is required for a virtualized application to run within the native desktop OS. Med-V creates a lot more overhead than App-V does. When you also consider that Med-V doesn't require hardware-enabled virtualization (Intel VT or AMD-V), you can begin to understand just how much overhead Med-V could add.
It is generally advisable to package applications with App-V and to use Med-V for applications that just won't work with App-V. As time goes on, you may eventually be able to phase out or upgrade apps requiring Med-V so you can use App-V to virtualize all of your applications.
ABOUT THE AUTHOR:
Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. He has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer, he has written for Microsoft, TechTarget, CNET, ZDNet, MSD2D, Relevant Technologies and other technology companies.
This was first published in May 2011