Nationwide is running about 1,500 Linux-based production applications -- mostly new ones -- on the mainframe, Vincent said. That is helping to hold in check the growth of the insurer's installed base of 6,000-plus servers, and the company expects to save about $15 million over three years by moving more applications to the mainframe.

In addition, the Unix group has gotten more comfortable with the changes, according to Vincent. Internally, he said, it has reached the point where Nationwide's Unix and mainframe staffers "are now part of the Linux/Unix team."