Desktop virtualisation, also known as VDI (Virtual Desktop Infrastructure), is THE technology that everyone is currently talking about. Influential analysts like Gartner, have blazed the trail and laid out the considerable benefits of this approach. These include the fact that operating systems and applications are not directly installed on user desktops but on servers, which means that IT managers can significantly reduce the administration burden of managing individual desktops.

At the same time, the user has the same experience when starting their computer and sees the usual desktop. Nothing changes, but in fact they are actually accessing an image, or virtual “representation” of the system (i.e. Windows® 7). This image is linked to the data-centre where the system is actually hosted.

Let’s take an example of a company with 1000 traditional PCs installed with Windows Vista that wants to upgrade its users to the new Microsoft system version. By using a VDI infrastructure, the move to Microsoft 7 operating system for all 1,000 desktops can take place in a few clicks on your server infrastructure and users will see Vista replaced by Windows 7 on their desktops the next time they boot up. The ultimate solution of course is to completely replace traditional PCs with thin clients, which are less expensive and need less energy. Thin clients require nothing more than the part processing the virtual image to operate.

VDI and Server Based Computing: What’s the Difference? 

All this sounds great but there are a few things that are holding back its widescale adoption. At first glance, the technology looks suspiciously similar to an older technology: Server-Based-Computing (aka application virtualisation or application publishing). Server Based Computing is based on applications working on remote servers and relaying the virtual image to the user’s desktop, only the applications are virtualised, not the whole operating system, which is not the case with VDI.

This difference is fundamental: SBC is used to manage application lifecycles, especially for installing the latest software updates, whereas VDI generally keeps the applications anchored firmly within the operating system. Many of our customers tell us that they are hugely impressed by the benefits of VDI technology but have given up after an initial test because they struggled to maintain applications or to reach the same level of service that they enjoyed with their “old” SBC technology.

Another disadvantage is the cost of the VDI infrastructure associated with migrating to a new operating system. The main difference relates to the storage costs which are quite high for VDI but nonexistent for SBC. For a typical office environment with 200-300 users, not less than 10GB and 1GB of RAM are required for each user. By comparison, SBC only requires 200MB of RAM and no storage space for the desktop.

IT managers, already worried by the need for a different approach to managing application lifecycles with VDI, become even more concerned once they receive the quote for the full architecture. Of course, the overall acquisition and management costs will be lower than for a traditional infrastructure but on balance SBC looks like a better bet.

Is VDI only a flash in the pan? 

On the contrary, VDI makes most sense when combined with SBC, where it has two key benefits: the ability for complete desktop personalisation based on the user’s needs (particularly important for certain types of users) – and total operating system compatibility, important for the efficient functioning of certain applications, which can produce incompatibilities when the application is working on the server in SBC mode.

The combined operation of VDI and SBC, for an IT Director managing 1000 desktops, will involve selecting and adapting their approach to virtualisation dependent on the needs and usage of his company. They can start by centralising and virtualising applications, then move on to desktop virtualisation on a case by case basis, when SBC is not suitable. And even when using desktop virtualisation, they can use SBC technology to maintain application lifecycles inside the virtualised desktop. A combination of the two technologies is therefore the best possible approach to meet users’ expectations, which are becoming ever more diverse.

So to sum up: the best approach toward VDI is to virtualise your applications as soon as possible, and then introduce desktop virtualisation gradually in response to your specific needs.