Linux boosts mainframe's appeal

Considered, at the least, moribund for the past decade, the mainframe sector has made a resurgence of sorts during the past year in its guise as a high-end server platform. Its success in this space has not gone unchallenged, however. Market-leading Unix server vendors are countering with their own big box antidotes for server sprawl.

For its part, IBM Corp. is trying to leverage its recent focus on Linux by marrying that operating system with its zSeries mainframes to meet what IBM officials believe is a potentially explosive demand for server consolidation.

Meanwhile, server vendors such as Sun Microsystems Inc. and Hewlett-Packard Co. are striking back at this obvious threat to their Unix businesses by touting new generations of high-performance servers, which they say make more cost-effective hosts for server consolidation than mainframes.

Linux on the mainframe is not an entirely new phenomenon. IBM first announced support for it on both the S/390 and zSeries mainframes in 2000, running under the company's proprietary operating systems for those platforms. However, IBM took a big leap forward at the beginning of this year when it announced a version of Linux that would run directly on the zSeries machines.

IBM's move provides a clearer path for Linux applications developers. Instead of operating through Posix-compliant application program interfaces (APIs), as they would have had to do if they developed for the earlier version of mainframe Linux, they can now easily port Linux applications developed for other platforms onto the mainframe. All that is needed is a comparatively simple recompile of the application's software code.

A good indication of the renewed interest in the mainframe is the attention being paid by third-party software developers. According to market watcher Giga Information Group Inc., those developers' enthusiasm for the IBM mainframe platform is at levels not seen since the 1980s.

Stacey Quandt, Giga's industry analyst for Linux and open-source software, said a "significant percentage" of the more than 500 IBM mainframes running Linux globally are new machines, which means customers are choosing those machines instead of other platforms because of the native version of mainframe Linux.

More precisely, the main reason Linux on the mainframe seems to have caught on is IBM's Virtual Machine (VM) technology, said John Phelps, a vice president and research director for servers and storage at Gartner Inc. VM allows users to partition the system in software, so that hundreds of Linux server images can be created on a single mainframe. Each server shares the system's processors, memory and data channels with virtual high-performance TCP/IP connections linking them.

"In many organizations multiple servers are now needed for a single application," Phelps said. "It's not just one server per application anymore. This server sprawl is getting out-of-hand, and Linux on the mainframe offers an attractive environment in which to consolidate things."

Chuck Gowans, e-business project manager at the Agriculture Department's National Information Technology Center (NITC), helps run a facility that provides information technology services such as file sharing, data mining, disaster recovery and network monitoring for hundreds of thousands of users in the USDA, Forestry Service, Federal Aviation Administration, Coast Guard and others.

NITC has done "significant testing" of Linux solutions on the mainframe and is close to running production versions for several of its clients, he said.

"This appeared to us to be the first truly available solution for transporting midrange servers to a hot site," a situation many agencies now need to consider for contingency planning and disaster recovery purposes, Gowans said. "The only way in the past that agencies would have been able to do [this] was to buy duplicate servers, but no one has the money to do that now."

In contrast, he said, a single mainframe can host multiple backup servers through its partitioning feature. An added advantage is that each server automatically becomes part of the mainframe-based enterprise architecture and can use all of the resource sharing capabilities that it offers.

NITC started testing solutions about a year ago, Gowans said, and some applications are close to production. In some cases, only the business models that customers will use to justify paying for that service — such as the hot site coverage — need to be ironed out.

Not surprisingly, Unix server companies disagree with this approach. Sun is even basing a business on what it believes is a trend in the opposite direction — traditional mainframe applications being hosted on servers.

"We think the thesis of running multiple copies of servers on a single machine is flawed, and our alternative is to run applications on much bigger servers," said Don Whitehead, director of Sun's Mainframe Rehosting Initiative. "We also think people are looking to take traditional applications and extend them into more modern [systems]. And the principal driver for that is cost reduction."

The cost of running a traditional mainframe environment "is really high year-on-year," he said, so Sun is offering to take the "huge investment" of applications custom written in the mainframe's Cobol and place them on Unix-based servers.

At the same time, organizations that take this tack will still have server space available for other uses, such as Web-based applications.

Bill Boggess, chief of the access and authentication technology division at the Defense Manpower Data Center, said his organization began migrating from IBM mainframes to Sun servers about five years ago. Now, most of the center's hardware is Sun-based.

"It was monetarily justified at the time because we were renting space at an EDS data center while at the same time we were sharing the cost of a mainframe at the Navy Postgraduate Center," he said. Upgrading by adding more machinery and renting space at the EDS facility would have been very expensive, and the cost of the Sun machine "was significantly less," he said.

The decision was also made easier because, by then, Sun was using technology that promised much of the same production services, such as partitioned domains, that the IBM mainframes offered, Boggess said.

Putting Linux onto mainframes does not mean that people will turn from servers to the bigger machines, Phelps said. There are some reasons — in particular the large upfront costs of a mainframe — that will cause many people to shy away from the solution, he said.

But it will stem some of the movement away from the mainframe platform, he said. For IBM — which Phelps believes has been as surprised as anyone at the success of mainframe Linux -that's reason enough to pursue the business.

Robinson is a freelance journalist based in Portland, Ore. He can be reached at

About the Author

Brian Robinson is a freelance writer based in Portland, Ore.


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