I think we can all agree that end users leverage applications while they interface with desktop operating systems. For years we have heard about small, large, fat, thin tall, short desktops in all kinds of colours. We have been told countless ways that users can access, touch, manipulate, and move these desktops, but what is often lost in the shuffle of all the madness, is the importance of the application itself.

In the past, the application ‘lifecycle’ was all about products like Microsoft’s SMS and the ability to wrap applications as an MSI. Those packages could then be delivered to endpoints where individual unattended software installs happened natively. The magic was ultimately in the controlled administration within SMS/SCCM and the ability to remove or uninstall the deployed applications, thus maximising efficiency within the enterprise desktop environment. Over the years various technologies attempted, unsuccessfully, to improve upon the MSI workflow.

Companies like Citrix optimised the “Application Remoting” concept, by hosting applications on centralised server workloads, while providing controlled remote access to users. The Application Virtualisation concept emerged as a true innovative game changer and was quickly adopted by enterprise production environments. The ability to isolate individual applications from either other applications as well as the operating system itself was, and is, truly impressive. Let’s take a look at application virtualisation and application layering as two noteworthy ways to delivery applications in today’s demanding desktop environments.

Application Virtualisation

Application Virtualisation solutions isolate the corresponding applications from both the host operating system as well as other applications. This is often achieved by creating a “bubble” or container that the application resides in. Inside this bubble, the application interacts with a proprietary unique mini “environment” where the application makes a request and gets an acceptable response, after which it functions normally. Essentially the corresponding applications think that they are installed or configured on the native operating system, but in reality they are hovering just above the host operating system in this isolated virtual bubble.

The corresponding virtualised applications are often communicating with the host operating system through a natively installed agent. Normal functionality of the corresponding applications is maintained through standard operating system features like file associations and services. One important aspect of the application virtualisation process that often gets overlooked is the elimination of the native application install procedures. After the virtualised applications have been deployed, they are ready for use immediately. The typical application install and configuration is only necessary once during the original package creation process.

Individual virtualised applications are often stored on network based file shares. Virtualised applications are deployed to endpoints using various trickle streaming mechanisms for offline use, or can be launched using a shortcut directly from the network based file share. Some applications, often based on the individual code framework, do not interact well with application virtualisation solutions. It is this challenge that application virtualisation solutions are not capable of single handedly supporting an enterprise application strategy. Additional solutions are often required in an effort to achieve a complete strategic application solution.

One example of a real world use case for an application virtualisation solution like Microsoft’s AppV, centres on application compatibility problems when attempting to deploy software within a Citrix XenApp environment. Sometimes Application A does not play nicely with Application B and the standard work around was to simply publish Application A and Application B on separate XenApp instances. With Microsoft’s AppV, there is an alternative where you have an opportunity to virtualise either Application A or Application B, decoupling the individual applications from the host operating system.

By leveraging AppV, the corresponding packages have limited visibility of the other conflicting application, and subsequently less chance of application conflicts. The need for separate XenApp instances for both Application A and Application B scenarios has been alleviated through the use of an application virtualisation solution like Microsoft’s AppV.

Application Layering

Application layering solutions take a slightly different approach compared to application virtualisation solutions. During the application layering creation process, a virtual hard disk in the form of either a VHD or VMDK is created and stored on a network file share. Once the virtual hard disk has been created, the normal application install and configuration is essentially redirected to this new virtual hard disk. Just like a puzzle piece, placed into its corresponding location within a puzzle, the new application layer virtual hard disk is connected to or attached to the corresponding operating system.

This puzzle piece or application layer can be attached to and removed from the corresponding operating system without effecting existing processes. At this point both the corresponding operating system and the application think that it is installed natively. Unlike application virtualisation solutions, where the application has to communicate with the corresponding operating system through the proprietary “virtual operating system”, the application within an application layer is communicating with the actual operating system, like it is “natively installed”, which provides for higher compatibility rates across many enterprise applications.

Similar to application virtualisation solutions, application installs are only necessary once during the application layer creation process. Application updates can either be applied to application layers or as real time events through an application layer temp folder within the user’s environment. Application layers are configured and stored in a few different formats, Microsoft’s virtual hard disk (VHD) and VMware’s virtual machine disk (VMDK). Ultimately which virtual disk format leveraged will be decided by many factors, not the least of which is the existing EUC infrastructure.


Early analysis suggests that application layering solutions have the potential to provide for higher conversion rates. However, a percentage of applications are unable to be virtualised using application virtualisation solutions, primarily because of an inability to communicate with the unique isolated environment within the bubble or simply the way the legacy application was coded.

Application isolation as described above is the primary difference between application virtualisation and application layering. It is the best and often most challenging aspect of this technology process. Application layering by comparison provides much needed portability considering the application has simply been redirected to the virtual disk. No changes have been made to the expected application workflow. When reconnecting the application layer, the operating system and native applications simply recognize that this new application layer is just another natively installed piece of software.

A real world use case for an application layering solution, like FlexApp from Liquidware Labs, focuses on developer applications. These applications have a tendency to be very large and hard to support. One often forgotten aspect of the supportability challenge around developer applications is the time required for installs and subsequently reinstalls. By leveraging the FlexApp layering technology, the developer application can be deployed to the endpoint without the need for the standard install. Within the FlexApp layer the application is already configured and ready to go.

Customers Looking For Direction

Across the enterprise application landscape there are many challenges to be solved. There is often no one tool that provides a complete fix to the issues. Based on the strengths and weaknesses of both application virtualisation and application layering solutions it has become clear that both solutions are great individually. Ultimately tools like Microsoft’s AppV and FlexApp Layers from Liquidware Labs are better together when attempting to achieve as close to a 100% application solution.