IBM will begin offering a service Monday that lets customers buy Linux computing capacity from Big Blue in much the same way they buy kilowatt hours of electricity from the power company.

With its Linux Virtual Services, IBM will sell the computing power of its mainframes, charging $300 per month for each "service unit"--about a third the computing capacity that a typical single-processor Intel server can provide, said Warren Hart, director of offerings for IBM's Global Services division.

With Intel servers costing less than $1,000, that may not sound like much of a cost advantage, but IBM's service includes server management and other tedious but costly chores and can help customers adjust to spikes in demand. Customers can tap into the IBM servers as if they were just another system in the corporate network, Hart said.

The service is one of the clearest examples of the move toward "utility computing," a trend that IBM rivals Hewlett-Packard and Sun Microsystems are also advocating. By pooling large numbers of servers connected over the Internet, these computing companies envision a future in which customers don't have to worry about the headaches of administering complicated computers, just as they don't have to know how to run a power plant today.

"In the traditional model, if I need to run an application, I need to get a server, pay for it, and buy enough server capacity for what will be the biggest minute of the biggest day of the year," Hart said. "In this model, I only buy as much as I need on average, not peak."

IBM doesn't yet have customers for the service, which will be available globally on Monday. But Big Blue has been discussing pricing with some potential clients.

One potential client, who had about 10 Sun and Intel servers, was spending around $75,000 a month for management, power, floor space and hardware, Hart said. Buying the necessary service units from IBM for the job costs $60,000 a month, he said.

IBM is beginning with SuSE's version of Linux running on its mainframes but plans to expand in the future to offer its z/OS mainframe operating system and, likely, other IBM servers as well, Hart said.