Feature

A recent Gartner (News - Alert) report compared four methods of delivering applications in Virtual Desktop Infrastructure (VDI) and found “application

layering” to be the best. Gartner’s analysis is boosting interest in this already-hot new desktop and application management technology. With this latest validation, vendors are quick to include their products in the layering category. However, to distinguish effective layering solutions from products that just “check the box,” IT organizations must understand what desktop layering is, and what essential requirements layering must meet if it is to truly overcome the challenges of delivering and managing Windows desktops in the cloud.

What is layering?

Layering is an advancement that enables virtual machines to be created and managed from distinct, modular building blocks, or “layers.”  Each layer is a virtual disk that can represent the Windows OS, individual applications, or user/machine personalization.  File system and registry virtualization technology merges the layers together to create a virtual C: drive for each VM. There are many benefits to this approach:

• Simple application delivery.  Applications can be delivered to many virtual machines from a single installation point. The layering process is as simple as installing an app on a physical PC.  Unlike traditional application virtualization, which isolates applications, layered applications look and feel as if they are locally installed, enabling full interoperability.
• One instance of Windows and every application to patch and update. Layers can be updated centrally as often as needed without affecting the contents of other layers. Updates are automatically propagated to all virtual machines without reinstallation.
• Disk space savings. The same virtual disk file that stores each layer is shared by many VMs, cutting space requirements upwards of 80% compared to traditional methods.
• Full personalization, including user-installed apps. Persistent and non-persistent desktops are provisioned from the same layers, so both desktop types are storage-efficient and easy to manage.
• One management console. Separate tools for desktop provisioning, image management, application delivery, personalization, disk space savings, and desktop break/fix are no longer needed, thereby reducing VDI project complexity and risk and enabling Tier 1 IT staff to manage virtual desktops.

Essential desktop layering requirements

Considering a layering solution for your organization? Here are five essential requirements. 

Layer everything, including the OS

Desktop layering must be able to layer every component of the desktop above the hypervisor – Windows OS, Applications, and Personalization. Some solutions only address personalization layering or application layering. These partial solutions ignore the part of the desktop that changes most often – the Windows operating system itself. They are also incompatible with OS-dependent applications such as Internet Explorer, since they are unable to resolve OS layer conflicts. An effective layering solution must be able to package and deliver Windows as a layer to make OS patches just as easy as application changes and to ensure that OS-dependent apps work without failures.

When evaluating a layering solution, be sure to test the ease with which you can layer Windows, apply OS service packs and hot fixes, and layer Internet Explorer along with other OS-dependent apps.

Support layer interoperability

A key benefit of layering is to simplify desktop and application deployment for IT by enabling layers to be assigned to any desktop in any order or combination. Another key benefit is that the many applications and plug-ins that need to interoperate can do so, leveraging the fact that layered apps appear as if they are locally installed (not isolated like traditional app virtualization).

Some layering solutions require that IT administrators artificially group apps that need to interoperate in the same layer. This re-introduces the very complexity that layering is supposed to eliminate. App delivery times will increase as IT professionals are forced to anticipate what apps need to be packaged together. Layer “sprawl” will occur to account for the many different app combinations that exist in the real world.  

Be sure to test whether applications such as Microsoft Office, .NET (News - Alert) applications, QuickBooks, and plug-ins in different layers can interoperate – and that apps will “just work” the same as if they were hand-installed on each virtual desktop.

Layer any application

Broad application compatibility is supposed to be a major advantage that layering has over traditional approaches to app delivery (e.g., application publishing or application virtualization). However, some layering solutions do not support all applications and recommend that unsupported apps are delivered as part of the Windows image.  This re-introduces the complexity and Windows image sprawl that layering is supposed to eliminate. Effective layering solutions must enable IT to package all applications – including those with boot-time drivers and system services, and those that must stay running when a user is logged out.

Consider whether PDF writers, speech recognition and dictation solutions such as Dragon Naturally Speaking, printers, scanners, antivirus, video surveillance, Single Sign On solutions such as Imprivata OneSign, and connection brokering software such as Citrix (News - Alert) Receiver and VMware Horizon View client can all be layered.

Manage the desktop lifecycle

Layering isn’t just about delivering apps. It’s about managing the lifecycle of a virtual desktop in ways that weren’t possible in the world of physical PCs. An effective layering solution must be able to track all changes to OS, App, and Personalization layers, with full audit records for compliance. Administrators must be able to “undo” patching mistakes simply by rolling desktops back to an earlier version of any layer. Multi-site VDI deployments must be accommodated with distributed layer replication so changes made centrally can automatically be propagated to thousands of desktops.

Determine how easy it is to track updates to layers, repair user mistakes (by reverting to earlier versions of the Personalization layer or by forcing IT controlled Application layers to take precedence) and undo patching mistakes by reverting back to earlier OS or Application layer versions.

Reduce complexity

According to Gartner, complexity is the #2 enemy of VDI projects. Layering should reduce complexity by enabling all desktop and application management functions to be simplified and operationalized through a single console. An effective layering solution provides all VDI management services in one, easy-to-use solution that can be mastered by Tier 1 IT staff.

Test whether service desk staff and Tier 1 IT administrators can perform all of the functions that are required to operationalize the day-to-day management of virtual desktops. 

Layering is more than a marketing term. IT professionals looking to overcome the challenges of desktop and application delivery and management in the cloud should consider these requirements when considering or evaluating a layering solution.