This post is the first in a series in which I will explore the advantages, the disadvantages, and the essential features of application virtualization solutions. I will also review some products which will make you realize how different the approaches to application virtualization are. You’ll find the links to all articles in this series at the end of each post. German speaking readers might also be interested in my introduction to application virtualization in the magazine Computerwoche.

Wikipedia defines it application virtualization as “an umbrella term that describes technologies that improve application compatibility and manageability by encapsulating applications from the underlying operating system on which they are executed.” The main idea is to run programs in a virtualized environment on a desktop system.

The difference between hardware virtualization solutions, such as VMware Workstation or Virtual PC, and application virtualization is that in the latter case the underlying operating system, the host if you will, is executing the program. But it seems to me that there is no clear dividing line between the different virtualization solutions. For example, you could say that Vista supports application virtualization as well, because it can virtualize folder structures and the registry for legacy apps. Hence the virtualization solutions differ only with respect to the objects they virtualize. Some virtualize a full-blown computer and others only the programs folder.

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Some days ago, I posted an overview of application virtualization which contained a list of several solutions. Some readers referred to additional tools and so I created a new list. I suspected that there might be more of them than the four I was aware of, but I was quite surprised by how many different application virtualization solutions there actually are. Virtualization.info compiled a more comprehensive list. However, it contains solutions that are not available anymore in this form, because they have been purchased and altered by their new owners. Thus, I created a new list and added a short comment to each product.

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This is the fourth post in my series about application virtualization. One of the products I listed in my last post was Xenocode Virtual Application Studio. Since then, I’ve tested this tool and was a bit surprised how easy it is to handle.

However, my first attempt to install the tool failed. The MSIInstaller complained that “C:\Program Files\Common Files\ODBC\Data Sources\” was missing. It was a Vista machine and so I thought it was a compatibility issue. Installation under Windows XP was done in a less than a minute. A few days later I tried it again on the same Vista PC and that time, the installation ran through without problems.

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This is another post in my series about application virtualization. More than a year ago Symantec bought Altiris, a vendor well known for systems management. I was quite surprised when I heard about the deal because the look and feel of Altiris products is somewhat different from Symantec solutions. This also applies to Altiris’ Software Virtualization Solution (SVS). I tested the tool and have shared some of my insights in this post.

I encountered the first problem when I wanted to download SVS. The download page showed four different file names which all sounded quite similar: Software Virtualization Solution 2.1 Logon Hook, Software Virtualization Solution 2.1 SP1 Integrated Installation, Software Virtualization Solution 2.1 SP1, and Software Virtualization Solution 2.1 SP1 Professional. There is a short note which is supposed to clarify what those product names mean, but I must admit I didn’t really understand it, so I downloaded the professional version.

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It has been a while since I posted the last article in my series about software virtualization. I have been working on a German article about this topic. During my research I learned new things which I am going to share in the next posts in this series. Today’s post covers the advantages of application virtualization. Of course, there also disadvantages which I will address in the next post.

No installation required: Installing an application on hundreds or thousands of computers is prone to error. Application virtualization simplifies software deployment.

Application retirement simplified: Getting rid of an app in your whole network is much easier as well. Since virtual apps just have to be deleted, uninstalling them is usually not required.

No more application conflicts: Sometimes installing an app corrupts another app. Application virtualization helps reduce the risks of application conflicts.

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Two weeks ago I reviewed Symantec’s application virtualization solution Altiris Software Virtualization Solution (SVS). In that review I described how virtualized apps can be created, I explained the layer concept, and I outlined how layers can be activated locally or remotely via the command line. Symantec offers a more professional way to deploy such virtualized apps: the Altiris Streaming System. Streaming means that only those parts of an application that are actually required to run the functions accessed by the user are transmitted to the client.

Symantec purchased AppStream some months ago and renamed their streaming solution. It is a bit strange that the new name contains “Altiris,” because this is another company recently acquired by Symantec. It seems like Symantec wants to keep the well-known Altiris brand alive. Like AppStream, Altiris Streaming System 5.2.2 allows you to stream not only virtualized Altiris applications (SVS apps), but also “conventional applications.” The corresponding packages have to be created with the Streaming Composer (a tool that comes with the Streaming System). There are three ways to package conventional apps, i.e. programs that are not virtualized. You can import an MSI file, track the application’s installation procedure, or create snapshots before and after the installation of the application. I won’t discuss streaming of conventional apps in this article because I want to focus on application virtualization in this series.

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My list of advantages of application virtualization did get quite long. My list of the disadvantages is shorter which doesn’t necessarily mean that the upsides outweigh the downsides.

A new complexity layer: Most Windows apps were not developed to run in a virtual environment. This might cause unforeseen problems. Whenever problems occur, you will wonder whether the app itself or the virtualized environment is the cause.

Vendor might deny support: If you tell your vendor that you are running their application in a virtual environment, they might deny support.

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When I started this series I thought application virtualization solutions to be rather simple tools. In the meantime, I tested some of them and read quite a few white papers about the topic. I discovered that there are far more products than I imagined and that the technological differences between the different solutions are substantial. In this and the next article I will summarize all the features that I am aware of.

Thus, if you have to evaluate some of the products, you can use this feature list to make sure that the solution of your choice supports everything you need in your environment. This post covers the conceptual differences between the various application virtualization products. In my next my post I will discuss the special features. Please note that it is not always obvious to which list a certain feature belongs.

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The features of software virtualization solutions that I address in this article are special in the sense that they don’t stand for conceptual differences. Nevertheless, they might turn out to be important or even decisive for your environment.

Settings: You might want to allow end users to configure their applications or install plug-ins by themselves. This means that they have to have the ability to modify the virtual environment. The various products solve this problem in different ways. Some tools allow you to store these settings on a server, thereby supporting application roaming.

Linking: This feature is related to the one above. Some products enable you to link virtualized apps. For example, one virtual environment could host the .Net Framework for .Net apps running in other virtualized environments. This feature can also be used to deploy add-ons. The more sophisticated solutions enable you to centrally manage the links between virtualized apps for your whole network. For instance, you could assign the Google Toolbar to a certain user group with just a mouse click.

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It seems that this was the longest series I ever wrote in this blog. The more I learned about this relatively new technology the more I was fascinated about it. By the way, German speaking readers might be interested in my new article about “Applikationsvirtualisierung” at Computerwoche. This post is probably the last one about software virtualization for the moment, although I might review another product sometime later. There might also be an article about the results of this poll.

I don’t want to influence your decision too much, thus I will keep this post short. I just want to add one further note. The funny thing about application virtualization is that it brings us back to the pre-Windows period. Do you remember the good old DOS times when applications were residing on a Novel Netware server? No installation was required on desktop computers, the term “registry” was only associated with public authorities, and administrators (called supervisors at the time) didn’t have the slightest idea that, only a few years later, Microsoft would send them to “DLL hell!”

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The results of my last poll are somewhat surprising. I asked if you plan to introduce an application virtualization solution in your organization. 69% of you responded with “yes.” It appears that more admins than expected know about the benefits of application virtualization. However, one should know that the participation was lower than in my other polls.

I admit that I only had a vague idea of application virtualization before I actually started testing different products. It was only when I saw how easy it is to virtualize applications that I became more interested in this technology. I suppose the relatively low poll participation can be explained by the fact that many admins don’t really know what application virtualization is. Thus, they just ignored this poll when they stumbled across it. Perhaps if I had added a third possible answer like “I don’t know,” participation would have been higher.

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