The Many Faces of Desktop Virtualization
It can be argued that VDI is a one-off use case that VMware invented many years ago for its ability to host a virtual copy of a desktop operating system in the datacenter. In other words, taking what the company had already proven for server operating systems and attempting to recreate the same magic (and assumedly ROI) for the desktop operating systems.
Since then, Citrix has also entered the space for the hosted virtual desktop (HVD), arguably what VDI is all about, and there are other offerings from other organizations such as Quest that are also driving home the concept of HVD.
Now, there are other technologies in the field of desktop virtualization that are used to (you got it) virtualize the desktop:
Operating System Provisioning:
OS provisioning can be delivered to either VMs in the datacenter or physical PCs at the desktop. An always-on network is required for these scenarios, which is why the laptop use case is not one that's preferred. Also, if this is to be delivered to bare-metal desktops, there is a significant issue in terms of hardware support: The hardware must support the boot options via the Citrix model, and the image that is shipped to each PC will most likely need every single driver known to man in order to guarantee that the OS will function correctly for the specific target hardware once it finally gets there. Citrix Provisioning server, Teradici PCoIP, HP's RGS solution are some examples.
Remote Desktop Services:
Of course there are still Remote Desktop Services (RDS) that may or may not include the Citrix XenApp layer. This has long been the de facto model to deliver server-based desktops or just to deliver standard Windows applications to users with little requirements at the client side. RDS continues to offer the best bang for your buck if ROI is all you are looking for, because there is far better scalability due to only one instance of the actual operating system running on the hardware (as opposed to VDI).
Client Hypervisors: Client hypervisors, of which Virtual Computer, Citrix, and Neocleus (now Intel) are examples, are very interesting as they potentially grant the ability for all of the management benefits of HVDs with the added mega-bonus of utilizing the client hardware for guaranteed performance benefits. That is, local hardware is always going to perform better than something hosted in a datacenter for desktop operations. Their challenge, however, is simply that the client hypervisor has a requirement on the actual hardware that will be supported. So the ideal use case of allowing a user to bring in her own laptop and run a VM on it is somewhat thwarted by the fact that it is extremely likely the user's device is not supported. Hence, the VM will not run on it.
Client-side Hosted Virtual Desktops: The client-side HVD technology vendors attempt to reduce this risk by enabling a VM to run on top of an existing operating system, so in effect there are two operating systems at the desktop that need to be supported. This of course can be minimized to reduce complexity, and it does eliminate the issue of not being able to run on all desktops due to unsupported hardware.
These technologies are also beneficial to the end user because they work in a disconnected state. As a result, the laptop use case can be realized more easily. MokaFive, RingCube and Wanova are examples here.
Both HVD and CVD (Client Virtual Desktop) require a change in mentality for the systems administrator, because there now is a lot more involvement needed to ensure that the operating system image and subsequent application packages are delivered to the user's desktop. Arguably the CVD is even more of a mind shift, because the IT administrator needs a significant amount of education before even considering this new model of IT management.
Application virtualization technology became a recognized form of desktop virtualization almost five years ago when Microsoft invested in a company called Softricity. Microsoft Application Virtualization (App-V) separates the Windows applications from the underlying operating system and (optionally) isolates the application from all other applications to enable multiple different (and potentially conflicting) applications to execute on the same Windows platform. The technology enables the administrator to package the corporate applications into containers that are then delivered (or streamed) into the desktop on demand, thus enabling a far more efficient form of application management. Besides Microsoft, there are many application virtualization vendors in the market space today (VMware's ThinApp and Symantec's vWorkspace, among others), all of which are helping the administrator build a more manageable enterprise application pool.
At the End of the Day...
As we can see, desktop virtualization is actually a whole lot more than just VDI, with complexity easily able to run rampant if we allow it. The one thing that remains constant, however, is that all of these technologies require a user virtualization solution to ensure that the user is serviced and his/her settings are always applicable regardless of the application or the model by which the application was initiated. The user experience is critical in all cases.
Posted by Simon Rust on 04/14/2011 at 12:49 PM