FAQ: Detangling virtualization

CNET News.com takes some of the mystery out of a complicated technology that has a steep learning curve.

For anyone buying servers or server software, and even many buying PCs, virtualization is getting hard to avoid.

The term typically refers to running multiple operating systems simultaneously on the same computer. It's long been around on high-end servers, but new software and hardware options mean mainstream users are starting to have to worry about virtualization. For example, both major commercial versions of Linux now have virtualization built in, and the next version of Windows for servers will, too.

Virtualization is complicated. But there are reasons you might want to take it seriously.

Mac users can run Windows to tap into the corporate e-mail system, or someone with a Windows Vista PC can run software that will only run on Windows XP. But in practice, the technology today is most likely to appeal to server customers, with advantages ranging from scrapping old hardware to cutting electricity bills.

Virtualization is a classic case of disruptive technology with a steep learning curve. For example, at the upcoming HP Technology Forum, there are 84 presentations to help Hewlett-Packard customers understand virtualization.

Here are some answers about what's happening today with virtualization.

What exactly does virtualization mean?
The term virtualization means that software is running on some sort of virtual foundation rather than the physical hardware it typically expects. Instead of a single operating system controlling a computer's hardware, the virtualization software controls it, providing multiple compartments called virtual machines for the operating systems to run in. Inserting a virtual layer can be liberating. For example, a running operating system can be moved to a fresh server if the one it's running on is suffering a failing memory bank or overtaxed processors.

Virtualization actually has been around the computer industry for decades, for example to run multiple jobs on mainframe computers or to hide the particulars of individual hard drives in a storage system. But now, it's no longer just a high-end technology.

Why is virtualization catching on now?
Because the technology is maturing and can help fix some common problems. Much of the credit for making virtualization a reality goes to an EMC subsidiary called VMware, which brought the technology to computers using mainstream x86 processors such as Intel's Pentium and Advanced Micro Devices' Opteron. In the first quarter of 2007, VMware's revenue grew 96 percent from the year-earlier period to $256 million, so there's no doubt the market is real and growing fast.

VMware built its business gradually. It began on desktop computers, where programmers could harmlessly test crash-prone new software in virtual machines or run Linux and Windows on the same computer, for example. In more recent years, the company's server software business became more lucrative as virtualization enabled customers to replace several inefficiently used servers with a single server running multiple virtual machines. Now the company is moving to a grander virtualization-based vision in which multiple tasks can run with shifting priorities on a pool of centrally managed machines.

Do I get a choice of suppliers here?
Plenty of competitors want a piece of VMware's action. First on the scene was Xen, an open-source project sponsored by Linux sellers, server makers and a start-up called XenSource. Virtual Iron is another start-up that's trying to make a business out of Xen. On the proprietary software side of the industry, Microsoft acquired a company called Connectix to counter VMware's products, but has had only modest success. The real fight will begin by June 2008, when the forthcoming "Longhorn Server" version of Windows gets updated with virtualization software code-named Viridian. Despite the fact that Xen is here now, VMware marketing director Bogomil Balkansky said Viridian is his top concern.

Although Xen got the jump, a newer open-source virtualization project called KVM has stolen some attention. Red Hat and another Linux rival, , have blessed KVM, and many Linux programmer heavyweights like its approach.

Another flavor of virtualization lets a single operating system be carved up into several virtual compartments, a lighter-weight approach that's been popular for Web site hosting. SWsoft's Virtuozzo, based on the open-source OpenVZ project, employs this approach, while Sun Microsystems' Solaris built the technology into its Solaris 10 operating system. Microsoft has said it's considering a similar move for Windows.

Featured Video