The joke used to be that IBM's mainframes were the useless dinosaurs of computing. None of IBM's rivals are laughing now. With Linux gaining popularity on IBM's zSeries, the mainframe is making a strong comeback.

This really isn't news though. In 2001, 11% of IBM's new mainframes were being sold with Linux under the hood. Today, according to Joan Meltzer, IBM's director of enterprise solutions for the zSeries, 17% of IBM's mainframe revenue is coming from Linux and that number is moving steadily upward.

IBM's not the only one doing well from Linux's big iron acceptance. Holger Dryoff, head of SuSE's American operations, says that SuSE's mainframe Linux; is accounting for almost 20% of SuSE's North American business. Other Linux companies--Red Hat and Turbolinux--support the IBM's zSeries, but SuSE is the leading mainframe Linux vendor.

So it is that IBM's keeps pushing forward with newer, stronger mainframes. The newest zSeries mainframe, the z990, aka the T-Rex, according to Bill Zeitler, general manager of IBM's systems division, will have three times the performance of IBM's last generation of mainframes. Whether it's really that fast remains an open question now, but at a cost of over a billion dollars over the last four years, IBM certainly intends the z990 to be the top computer in its class.

One of the biggest drivers behind both the mainframe comeback with Linux, says Meltzer, is server consolidation. "Companies, like Wisconsin Physicians Service Corp. an insurance company, have found that it's a lot cheaper to run multiple Linux virtual servers on a single z900 than to run 40 Intel-based servers." How much cheaper? Try on the order of over a million dollars a year in savings.

It's not just, she continues, that you require less administrators and hardware, it's also that administrators can start up and configure a new virtual server application in two or three minutes versus two or three days. That's a savings that any CIO can appreciate.

Another plus, especially for companies that outsource their computing needs, is that Linux on the mainframe makes it very easy to add, or subtract, computing power as needed with IBM's On Demand business plans. If a company needs more, for example, more server application power, with On Demand, IBM or the reseller can simply fire up another Linux server instance, copy over WebSphere and the appropriate code, and have another 'server' available for a customer within hours.

At the same time, more administration tools for Linux on the mainframe are appearing making it even more attractive for customers. Tivoli Management Portal, for example, enables administrators to over see a mainframe's performance and carry out reliability checks from a single desktop. Linuxcare, a leading Linux support company, Levanta; enables administrators to more easily control Linux instance provisioning, configuration and deployment while providing them with the tools they need for comprehensive change management.

What all this means for customers is that IBM mainframes and Linux are maturing together. In the past, running Linux over IBM's z/VM required top-of-the-line mainframe and Linux administrators. These new tools are bringing Linux on the mainframe to every day mainframe managers.

Linux, IBM, and mainframes are a combination that has worked well together so far and, from all signs, are going to work together even better tomorrow. As Ed Gauthier, Program Manager for Linux for zSeries, says, "I can't see how anyone can surive in mainframe business without Linux."