When the country heads out on vacation, Exxon Mobil Travel Guide LLC wants to be ready. The 2-year-old travel-planning business intends to launch an online service later this year that will let customers book and change travel plans on the road for a fee. The company last week signed a five-year contract to use one of IBM's utility computing offerings, Linux Virtual Services, to handle the online traffic.

The travel service already is migrating newly developed travel and database applications for its new Mobil Companion to IBM, which will host and maintain them on a mainframe running SuSE Linux.

The travel-planning business rents mainframe, storage, and networking capacity at an IBM data center and pays a monthly fee based on the number of service units it uses. Service units represent a combination of hardware, software, and networking resources. The company won't disclose the amount it's paying for the service, but IBM generally charges about $300 per service unit for Linux Virtual Services.

Linux Virtual Services was a good fit, CIO Paul Mercuro says. "We're a relatively small entity with a big name. I expect we'll have to ramp up dramatically, but I didn't want to invest in the infrastructure up front." IBM has created a virtual server on a mainframes that will run the travel service's mapping, hotel-reservation, call-center, and personalization apps.

A utility-based approach is a shrewd move, IDC analyst David Tapper says. When people travel, they look for bargains. "Now that people are used to using the Internet, you don't know what the volume will be."