Yet it also has drawbacks – particularly in terms of the additional capital investment required to deliver enough servers to support a VDI environment (see sidebar). With seven to nine virtual desktops supported per server CPU core and 1GB to 2GB RAM still required per server, most companies will need to bulk up their servers and storage infrastructure to bring their desktops under the data centre's wing.
Such considerations are unavoidable, and mean may companies will make the move to virtual desktops when it's a natural progression rather than a revolution, according to Trevor Clarke, senior analyst within IDC Australia's Infrastructure Group.
"A lot of Australian organisations have gone through a consolidation phase, bedded down their strategies and are looking at what to do with virtualization next," says Clarke, who recently surveyed local industry and found more than half of Australian organisations will be using VDI, although not exclusively, within a few years. Twenty percent are already doing so, he adds. "It's a matter of rolling it out and seeing that they're doing it for the right reasons."
When building a business case for virtual desktops, very real capital costs must be balanced against the projected savings from everyday management — and the ability to better execute complex or large-scale changes to the application and operating environment. As Wesfarmers in particular found, the ability to isolate desktop environments offers tantalising benefits by enabling the coexistence of different operating systems and application versions.
This is particularly useful in large companies with multiple SOEs, but it can also be used as a migration strategy that allows the maintenance of parallel desktops during an application switchover. This will make virtual desktops invaluable for IT managers staring down the end of Microsoft's Windows XP support in a few years, when they'll have no choice but to refresh Windows. In the intervening years, it's possible to move to Windows 7 and scrape a user's existing XP environment into a virtual machine so nothing outwardly changes.
Access to multiple desktops at once is one of the main reasons the Department of Defence has been outspoken in its support for the VDI concept, since many employees currently have several desktops each configured for access to information of a certain security level; virtualising these would allow access through a single device.
Access rights are another important benefit of virtual desktops. Since VDI technology is now integrated into existing management frameworks, it's possible to assign access to virtual desktops based on an individual user's access rights, job role, or ad-hoc requirements. Extend this to mobile devices and factor in the fact that virtual desktops retain their state at all times, and it becomes immediately obvious why virtual desktops are a good idea. An employee whose laptop battery dies while in the field, for example, could switch to his iPad, authenticate himself, and keep on working.
The right level of virtualization
In feeling out the opportunities of the virtualization market it's also worth considering 'application virtualization' technology, which wraps individual applications in their own virtual machines and streams them to user desktops.
"The traditional Office SOE is being disassembled," says IBM's Rugless. "Rather than having it all distributed and having to be managed so every update is loaded in a timely fashion, we're stripping the apps off and publishing them back through the network. The way the apps are stacked on the SOE provides the best performance.
This highly-granular approach, pioneered by now-Symantec subsidiary Altiris and also encapsulated in products like VMware ThinApp and Citrix XenApp, allows for easy distribution of new apps without fear that they will clash with the rest of the environment; this model can easily be extended to third parties to allow secure, streaming access to applications on demand. Expect to hear a lot more about application virtualization this year, since it – and the self-contained applications upon which it depends – is a core tenet of Apple's Mac App Store and the inevitable knockoffs enabling apps-on-demand app installation.
There is a downside: since the applications rely on the underlying operating system and hardware, this approach doesn't allow the same measure of device independence unless paired with a full virtual desktop platform as well. That's not a problem when all the devices you're working with are running the same operating system, but it can pose issues when you're trying to deliver, say, Microsoft Word to an iPad running Apple's A4 processor and the iOS operating system. Such situations require the streaming of both the applications and a suitable operating system on which to run them. Application virtualization sits aside two types of desktop virtualization — 'pooled' virtual desktops, in which a standard desktop image and applications can be delivered to many people — and 'assigned' virtual desktop model, in which each user gets a full desktop of their own that just happens to be hosted somewhere else.
Pooled desktops are easier to manage, but users tend to prefer assigned environments because they offer the customisation they're used to. Since each assigned desktop can be different, that approach can also ease the migration process if a company wants to scrape existing desktop images and drop them into a VDI container. This is possible using Microsoft P2V Migration for Software Assurance, VMware vCenter Converter, or Citrix XenConvert.