Stratus' main competitor among fault tolerant systems vendors is Hewlett Packard Co., which sells the NonStop system originally developed by Tandem Computers. Compaq acquired Tandem in 1997 and HP acquired Compaq in 2002. NonStop is also available as a triple-redundant system.

Gordon Haff, an analyst at Illuminata Inc. in Nashua, N.H., said some users still want triple-redundant systems. "It gives you a larger window to fix a problem," he said.

While Stratus and HP overlap in some parts of the fault-tolerant market, Haff believes Stratus isn't going after the very high-end of the market. HP has targeted high-end operations with its Itanium-based Integrity systems and its NonStop kernel operating system. For Stratus, "they're kind of real pitch is fault tolerance on a budget," he said.