With servers, the norm has been: any application likely to run constantly, such as Microsoft SQL Server or Oracle, requires its own processor. As a result, these applications must be licensed for multiple processors even though the extra horsepower often goes to waste.

With the advent of central processing unit (CPU) virtualization software, those requirements are changing. Virtualization software essentially creates an image of a processor's memory when an application is running. When an application requires more processing power, the virtualization software will steer the application to an available processor.

It makes sense to use this software if you are considering a major capacity upgrade.

Or if a software vendor insists, for instance, that its application running on a dual-core processor be licensed for each core. Virtualization can ensure that only one core runs the program.

Another trigger: multiple, seldom-used applications—perhaps for end-of-week or end-of-month rollups like accounting—where each application takes up a precious server along with a licensed copy of Windows 2000 and network software.

Still, virtualization sofware may not be right for you. Before you take the plunge, you must investigate whether your operations—physical layout, loads and applications—can meet minimum requirements established by virtualization software for network and server speeds, etc. Vendors include PlateSpin, SWsoft and VMware, now owned by EMC. There's even an open-source virtualization suite, Xen.

TOOL: The Return on Virtualization Software

CPU virtualization software, which enables a single processor to run multiple operating systems, promises lower operating costs and other benefits. Here's a worksheet to help you figure the return. The example assumes existing in-house servers with 25 processors running 10 different applications every day, such as 25 copies of SQL as well as a storage area network. INSTRUCTIONS: Fill in your own numbers in the column labeled "Your Company" and do the calculations described at left. Or click <"go.baselinemag.com/Dec05">here for our Premium Tools Library.

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