He said the data warehouse is used for every "major part" of the bank but critically for financial reporting, global risk management, and regulatory reporting, including Basel II compliance.

Spencer attributes the change to a culture of innovation in the bank, which is not just in one central group.

"[NAB] has a culture of open innovation," he said. "Could we use Linux inside NAB? We grabbed a consortium of partners in a room who coughed up hardware and support to find out."

The original project, called "Pinta" after the fastest of explorer Christopher Columbus' three ships, showed the bank it could move to Linux, but also showed what was missing, such as storage drivers from EMC Corp.

With the global data warehouse and "Super Mart" database in place, the bank has also experienced significant cost savings by moving to Linux on Intel and away from Solaris on Sparc.