Cost, Savings

IBM's mainframes typically cost more than $1 million, with the price rising as customers add features. Unix-based Web servers start at several thousand dollars and cost as much as several hundred thousand dollars. Consolidating server farms reduces the cost of personnel to manage the servers, the floor space to house the devices and the power needed to run them and associated air-conditioning, Mastrobattista said.

While many customers use mainframes for processing various types of transactions, some have been attracted by the inexpensive Linux operating system and the ability of mainframe operators to partition the machines, Mastrobattista said.

Entire server farms running corporate Web sites, file servers and the like can be consolidated on one mainframe, which IBM has touted in television advertisements that began this month. In one, dubbed ``The Heist,'' a frantic executive calls the police to report the theft of a vast roomful of servers, only to have a carefree underling remind him that all of the data was moved to a single mainframe standing in a corner.

More than 100 zSeries customers bought the mainframe with Linux, and others may have incorporated the software on their own, IBM said.

``It has been a very material factor in the resurgence of the mainframe,'' John Morris, IBM's vice president for zSeries sales, said in an interview. He declined to estimate sales growth for the current or future quarters.