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How application layering reinvents remote app delivery

VDI shops don't need to install applications within virtual desktops for apps to interact with the host operating system. Instead, they can deliver and manage applications separately using app layering.

Organizations looking for a little less isolation and more interoperability than application virtualization provides now have an alternative delivery method in the form of app layering.

For years, app virtualization has provided a way for IT to package and deliver applications to VDI clients, but some companies don't want the isolation inherent with products such as VMware ThinApp and Microsoft App-V.

Application layering provides a way to preserve many of the advantages of virtualizing an app, while addressing some of its limitations. As with traditional app virtualization, layering separates applications from the host operating system (OS), making them easier to implement and maintain. App virtualization tools strive to isolate applications, whereas layering products try to integrate apps with the OS, so they perform as if installed locally.

The technology is gaining steam in the enterprise, with application layering tools such as Citrix AppDisk, VMware App Volumes, Liquidware Labs FlexApp and Unidesk all available for IT to use in its VDI deployment. An app layer can support multiple applications and target specific users or groups, while also streamlining the apps' implementation and management.

App virtualization paved the way

Layering eliminates the interoperability issues that arise with app virtualization.

Application layering is sometimes referred to as a type of app virtualization, but they are distinct technologies. Virtualizing applications started out as a way to isolate apps from the host OS and from other applications to address any incompatibility issues. By isolating an application in its own container, IT could better control how other processes interacted with that application.

Additionally, application virtualization offered a way to provide on-demand app streaming to multiple endpoints, rather than IT installing applications on the golden image for a VDI deployment. If IT can't deliver apps independently of virtual desktops, then administrators often need to maintain multiple golden images to accommodate various departments that require different sets of applications.

The more golden images an organization uses, the bigger the task for IT to update and maintain them all, especially when admins also have to update the apps themselves. Application virtualization eliminated the need to constantly tinker with golden images and to repeatedly install applications.

How app layering is different

Layering takes a different approach to delivering applications than app virtualization. Tools such as Citrix AppDisk and VMware App Volumes deliver apps that run on one or more layers separate from the OS. Each layer is either a Microsoft Virtual Hard Disk or VMware Virtual Machine Disk independent of the OS, but not decoupled from it. From the perspective of the app and the OS, the application runs as if installed locally.

IT departments have a great deal of flexibility in how they implement application layering. For example, IT could create a layer for applications to distribute across the entire organization and then create another layer for each department. IT can assign a layer of apps to specific users or groups, or assign the layer based on other criteria, such as connection types or Lightweight Directory Access Protocol properties, depending on the layering product.

Layering eliminates the interoperability issues that arise with app virtualization, providing a higher level of compatibility across the VDI deployment. IT can layer device drivers, shell-integrated programs and other complex applications that aren't a good fit for app virtualization. To the OS, an application layer is simply another drive that contains natively installed programs.

App layering also offers many of the same advantages as virtualization, providing real-time application delivery from a single image. An administrator needs to set up an application only one time, without having to touch the golden image. Implementing, delivering, upgrading and rolling back applications are as quick and easy as with virtualization, but even more efficient because they act like native apps.

There are always two sides to a coin, though. Many organizations want the interoperability that app layering provides, but some scenarios still call for isolating an application. For those occasions, IT will need to use a more traditional app virtualization product such as App-V or ThinApp.

Application virtualization sometimes falls short

Although app virtualization is a useful method for delivering applications to users, the isolation that accompanies it presents challenges for IT because the applications can't interact with one another. Many applications need to be able to communicate and share data with antivirus software, device and kernel drivers, plug-ins or applications. In fact, the list of apps that IT cannot virtualize is quite long, ranging from internet browsers to development tools to a variety of productivity tools, leaving IT to search out other techniques for delivering applications in a VDI deployment.

The changing world of app delivery

With VMware and Citrix both in on application layering and a strong midmarket with vendors such as Liquidware Labs and Unidesk, it's a good time for IT to look into layering. Although app layering products are similar in principle, the exact approaches vary from one to the next.

Creating the layers themselves is relatively straightforward in most offerings, so when shopping around, IT should focus more on how the product manages dependencies and interactions between layers. Before deciding, be sure to thoroughly vet as many app layering products as possible, and try them out to ensure they deliver applications securely and efficiently.

It's still up in the air whether organizations can or should use application layering as their only app delivery method, but it's an area of end-user computing that is rapidly maturing. For now, IT should continue to virtualize applications that require isolation.

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