An average of 2.5 million subscribers are active on America Online at any given time, keeping some 800 RISC-based Unix servers busy managing log-ons, user name and password verifications, and parental-control activations. But some of those servers may be headed for retirement: The AOL Services division of AOL Time Warner is beginning several months of testing to determine whether blade servers using Intel chips may be a more efficient way to handle the load.

AOL Services has installed 56 IBM BladeCenter servers -- 14 "server-on-a-board" systems per chassis -- running Red Hat Linux 7.3 to route a portion of the Web traffic that's now handled by its Unix-based back-end routing servers. If they deliver the advantages in cost, scalability, and performance that Norman Koo expects, AOL will replace all 800 Unix systems with blade servers during the next five years. "Blades do more work, take up less space, and use less power," says Koo, executive director of corporate technology at AOL Time Warner.

The dual-processor blades include built-in Ethernet switches, and Koo says AOL will be able to run the systems for half as much as it costs to run its dual-CPU Unix servers. BladeCenter servers, which start at $1,879, will be generally available in November.

Koo says there may be other jobs for blade servers at AOL, as well. He says they may provide a more efficient platform for running data-warehousing applications.