Nonetheless, Seager said that KeyBank's core mainframe is under no immediate threat of being evicted by a Linux cluster.

The lack of plentiful banking applications for Linux systems also hurts the operating system's prospects, especially since banks tend to buy off-the-shelf software instead of building it themselves, said Brent Biernat, assistant vice president of networking services at COCC, an Avon, Conn.-based provider of IT services to community banks and credit unions.

The application shortage was cited by one bank IT executive as a reason why she remains 'very cautious' about Linux despite potential cost savings. Sufficient availability of third-party applications and 'robust operational monitoring support remains to be seen,' said the executive, who asked not to be identified.