We usually think of the processor chip as the brains of a computer, but its a mighty versatile brain. The same standard PC chips that run Microsoft Corp.s ubiquitous Windows operating system can just as easily run those geeky alternatives, Unix and Linux. Switch operating systems, and the computer takes on a whole new personality.
Indeed, lots of computer users keep multiple operating systems on their hard drives, and use special software to select the one they want when the computer reboots. Its called dual-booting, and its a handy way to try out various operating systems but not handy enough.
Say youre trying out Linux, but suddenly need to check your Microsoft Outlook appointment calendar. Its time to reboot and load Windows, unless you could somehow persuade your computer to run Windows and Linux at the same time.
And you can, with the help of software that can turn a single computer into two, three, or more machines, all happily coexisting inside the same box.
Its called virtualization software, and it works by placing itself between the computer and the operating system. Normally, its the operating system that directly runs the various bits and pieces of hardware. Instead, the virtualization software takes control of the machine, then parcels out resources like memory and processing cycles to the various operating systems. Each package of resources is a virtual machine, entirely separate from the others. Its as if multiple computers were churning away on a single motherboard.
This is all very advanced and very old. Big computers have done this sort of thing for decades. IBM Corp. embraced Linux partly because it will run as a virtual machine on a IBM mainframe, alongside the mainframes standard software. But virtualization hasnt been as popular on smaller servers and personal computers based on Intel-type processors.
But thats starting to change, thanks to VMware Inc., a California subsidiary of Hopkintons EMC Corp. VMware was launched in 1998 with VMware Workstation, a remarkable program that let a desktop PC run two or more operating systems at the same time.
We tried the most recent version on a desktop machine running Windows XP Professional, with an AMD Athlon 64-bit processor and 512 megabytes of memory. There were a few problems during setup, but once installed, the virtual machine ran Novell Inc.s Suse Linux 9.1 with hardly a hitch.
With the PC running two operating systems, we expected a sharp decline in performance. We were wrong. Both Linux and Windows ran nearly as fast as ever. VMware even connected the virtual Linux machine and the real Windows machine, so we could swap files.
VMware Workstation makes a splendid tool for Windows users seeking to sample the delights of Linux. Too bad about the price, though; $189 is far too high for the desktop dilettante.
Still, VMware isnt mainly after that market. The company has sold its virtualization software to about 5,000 major businesses, such as Google Inc., Merrill Lynch & Co., and Prudential Insurance Co. Virtualization lets these companies save millions, by using one computer to do the work of several.
Usually, companies run their important computing tasks on machines dedicated to that purpose. So an inventory control program runs on one server, database management on another server, accounting on a third, and so on.
But todays Intel-based servers are so powerful that one of them could easily handle all these tasks.
In most of these server environments, utilization rates are like 15 or 20 percent of the capacity of that server, said Howard Elias, EMCs executive vice president of corporate marketing. In other words, most of the computers power isnever used.
But install VMware on the server, and you can set up a host of virtual machines, each running a different task.
You could have Windows 2000, Windows NT, Red Hat Linux, all on the same server, said VMware president Diane Greene, who estimates that VMware generally lets users run 10 to 12 of their key business applications on a computer that previously hosted just one.
HIAWATHA BRAY / NY TIMES