…businesses to separate their corporate environment from personal applications, such as iTunes.
One of the challenges of desktop-based virtual machines is the fact that there has to be enough memory to run both the host operating systems and any guest operating systems.
In theory it might be nice, for example, to run one's online banking application in a virtual machine that is entirely secured from the rest of the operating system. Memory requirements, though, make that impractical at this point, Neil said. "That's a pretty significant tax to pay to do that," he said.
VMware is trying to make installing new virtual machines less onerous. Last week, VMware demonstrated "instant-on" streaming technology that began firing up a 410MB virtual machine when only a fraction of it had been downloaded.
Server-based virtual desktops, meanwhile, aren't necessarily completely interchangeable with regular PCs, though. For example, Microsoft's RDP doesn't currently support audio. Corporate IT might be happy that users aren't likely, therefore, to spend a lot of time watching YouTube videos, but audio support also is important for work tasks such as webcasts or internet telephony conversations.
Frank Sabatelli is a big fan of running virtual desktops on servers. As vice president of virtual engineering at financial services firm iQor, he has to set up new offices with hundreds of PCs for the call-centre services the company offers to clients, such as credit-card firms.
"We had technicians in the field who would have to redeploy 500 or 600 machines in a couple weeks," but the company couldn't keep up with competitors, Sabatelli said in a discussion at the VMworld show in San Francisco on Tuesday. With virtual desktop software from VMware, deployment of such an office takes 48 hours. "We got it down to under eight minutes per machine," he said.
One complication of virtual desktops is software licensing — in particular, Windows licensing. Only some versions of Windows may be installed on multiple virtual machines and, even then, moving a virtual machine from one machine to another poses complications.
"You could probably get a PhD in Windows licensing," quipped one executive who has to reckon with the issue.
Matt Levine, a web developer for blog-monitoring site Technorati, said his company makes extensive use of Parallels and of VMware's rival Fusion product for testing its site. "We're able to simulate different computing environments and different browser environments that our users are going to be using," Levine said. That vastly accelerates testing of new features, especially given that Internet Explorer 6 and 7 can't be installed simultaneously on the same machine, he said.
Virtual desktops are a natural fit for one company: Sun, which has for years advocated the idea of moving as much processing power as possible to central servers. This week, Sun announced Virtual Desktop Infrastructure Software 1.0, which goes on sale in October and incorporates software from its acquisition of Tarantella in 2005 and other products.
Sun's $149 (£74) software acts as a middleman that transports information from thin clients or PCs to the central servers' virtual desktops and back. It can use VMware's virtual-desktop software, connecting its PCs via Microsoft's transport mechanism or Sun's own technology — which, unlike Microsoft's, supports audio.
Parallels, too, is hoping not to be left behind in the Windows and Linux worlds.
The company is looking to bring over to its Windows-based program some of the consumer features it has on the Mac, such as Coherence, which allows programs from guest operating systems to appear as if they are native to the host operating system.
Although the Mac is where the most demand is today, Parallels spokesman Benjamin Rudolph said that, as Linux gains ground, there may be more reasons to run it alongside Windows.
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Desktop Linux is coming, he said. "It may not be the huge spike that people predicted five years ago, but it's coming."
Virtualisation means that people don't have to switch entirely to a different operating system. If people find even one Linux application that they really want to run, desktop virtualisation can make that feasible.
Rudolph said virtualisation also enables people to try out things that they might otherwise be afraid to try. An early beta version of a program or some other questionable application can be installed in its own virtual machine. If it works, great. If not, just delete the virtual machine.
"It's the ultimate pen with eraser," Rudolph said.
