When Parallels Desktop was released in June 2006, it opened the door for hundreds of thousands of Apple users to run Windows at the same time as they ran the Mac operating system.
It also introduced the masses to the notion of desktop virtualisation.
Virtualisation, until recently, has focused largely on the server, where the idea of enabling one server to act as many has clear cost benefits.
While Windows on a Mac is still the most widely known use for the technology, there are reasons why desktop virtualisation may soon expand into new areas.
So far, many of those areas are in the corporate arena, where businesses are aiming to offer more secure environments or perhaps run older in-house software that only works with older operating systems, while at the same time having desktops running modern operating systems. It also has benefits in terms of disaster recovery, provided the virtual machines are well backed up.
There are two main ways of carrying out desktop virtualisation. One is to run multiple operating systems on one PC. Another is to have one or more operating systems running on a remote server, with the desktop tunnelling in to those other operating systems. Technology such as Microsoft's Remote Desktop Protocol (RDP) pipes keystrokes and mouse clicks to the server and a view of the screen back to the user.
VMware offers technology for both desktop virtualisation approaches. Its Virtual Desktop Infrastructure takes the server-based approach, while two other options handle things directly on the desktop, one for power users and the other for standard cubicle dwellers.
Its workstation product is geared for power users, such as administrators who want to test software patches before distributing them across a company, said Jerry Chen, senior director of enterprise desktop software at VMware. Chen himself uses it to run three separate virtual machines: one for work, one for home and one for his Slingbox video player.
The one geared for standard users enables corporate administrators to provide locked-down desktop software, for example prohibiting use of printers or flash memory drives in cases where sensitive data is involved. It also lets the user pack up the virtual machine on a flash drive and continue working with it on another PC, provided that computer is capable of running a virtual machine.
Virtual machines could also prove useful in the home, letting a physical machine be carved into each family member's "own PC". Nowadays, typically, each member has a separate user account to segregate the programs and data, but a virtual machine would prevent, for example, a family youngster from wiping out dad's PC with a virus downloaded from some file-sharing service.
Start-ups enter the fray
While VMware is the dominant player, there are plenty of contenders in the desktop-virtualisation industry.
Citrix, which has years of experience with thin-client software, acquired XenSource in August for $500m (£250m), a move that provides it with software for virtual PCs on a central server.
And other start-ups are preparing to enter the fray. Qumranet, sponsor of the open-source KVM virtualisation software, plans to announce a product later this month that integrates all the technology necessary for setting up and running virtual PCs on central servers. Pano Logic, headed by former XenSource chief executive Nick Gault, announced its plans last month to use VMware server technology to create centralised virtual desktops.
Microsoft also sees desktop virtualisation, in its many forms, gradually becoming more popular among general users, but general manager Mike Neil noted that the technology is still probably a long way from being used by the majority of mainstream users.
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Comment: The right application of virtualisation
Server virtualisation has its benefits but it's at the application level where the technology can really make a real difference, says DataSynapse's Peter Lee
The company was an early player in desktop virtualisation, scooping up the Virtual PC business of Connectix back in 2003. The company has since made that product largely free, but chose not to participate in the Windows-on-Mac space, an area where Virtual PC was once the only game in town. On the PC side, though, there have been 2.5 million downloads of the product since February, with IT departments being among the most common users of the technology.
Others, including Intel, have proposed running security and management software in an administrative virtual machine that runs alongside a PC's regular operating system. It could, for example, monitor network traffic to guard against the spread of a worm.
Another idea is to use a virtual machine to segregate work and personal applications on a PC, allowing…
