Mainframe Linux can boost application uptime and reduce support costs. But users and analysts recommend acting carefully when choosing which applications to move to the open-source operating system and when training staff in the required skills.
The attraction of Linux on the mainframe isn't so much the low cost of licensing Linux or the fact that users can modify it and rely on a community of developers to fix bugs, users say. Instead, the big draw is the ability to combine Linux with the mainframe's proven reliability, speed and management tools to drive down the cost of running critical applications.
"We're not interested in just getting the least expensive thing on the market," says Randy Lengyel, senior vice president of MIS at Wisconsin Physicians Service Insurance (WPS), a health insurer. "We want something that is reliable, functional and has great customer service from the [vendor]."
Hitting the Sweet Spot
The sweet spot for mainframe Linux today is server consolidation -- replacing dozens or even hundreds of separate Intel-based Linux or Windows servers with a partition on the mainframe that dedicates a single processor, memory and other system sources to running Linux.
WPS created a virtual Linux server running on one 250-MIPS processor that was available within an IBM eServer zSeries 900 mainframe and did it at 40% of the cost of ordering, installing and configuring a new Intel-based server, says Lengyel.
A virtual server can be created within two to three minutes and deliver as much as nine times the throughput of a stand-alone server, he says. WPS, a longtime mainframe user, was drawn to running Linux on the mainframe as a way to leverage the mainframe's reliability and to keep support costs low.
The instability of its Windows NT servers was one reason why recreational vehicle manufacturer Winnebago Industries implemented Bynari's InsightServer groupware application for Linux on an IBM zSeries mainframe.
Dave Ennen, technical support manager, says he had to reboot his Windows NT servers once a week in an effort to improve their stability. But "on the mainframe, everything is geared to staying up 24 hours a day, seven days a week," he says.
Winnebago already had a mainframe (an IBM S/390 Multiprise 3000 Enterprise Server) and a staff skilled in IBM's z/VM, an operating system that can divide each partition in a mainframe into multiple software-based virtual machines, each running its own operating system and applications.
Rather than go through the expense of training his staff for the upgrade from Windows NT to Windows 2000 and Windows Exchange Server 2000, Ennen says it was more cost-effective to use part of his existing mainframe capacity and his staff's mainframe skills to run its Linux-based e-mail system. However, "if you were going to go out and buy a mainframe" just to run Linux, he says, "it's going to be a little hard to justify."
Many observers say users should be running at least 20 to 25 servers before even considering consolidation into a mainframe Linux environment. Some of the best candidates for consolidation are infrastructure applications such as file and print services, e-mail, domain name servers and Web servers such as Apache.
But not every application is a natural for mainframe Linux. Windows applications are a poor choice, since they don't run on Linux, although Linux equivalents are available in many cases. And applications that have complex graphical user interfaces or that perform complicated data analysis can use so much processing power that it's more cost-effective to keep running them on stand-alone servers.
Users have also been reluctant to move complex applications such as SAP R/3, which can take years to implement on distributed servers, onto a new environment. Although SAP AG has been among the first vendors to support Linux with its flagship products, Linux will represent only about 10% of new installs in 2003, says Manfred Stein, product manager for Linux Lab and Unix platforms at SAP.
Once you've identified applications to run on the mainframe, users and analysts recommend migrating them first to stand-alone servers running Linux. That's a good way to get support staff familiar with Linux before tackling the additional complexity of the mainframe, they say.
Training Unix veterans in mainframe Linux skills -- or Linux veterans in Unix skills -- can be one of the biggest challenges. Many organizations have one support organization for mainframes and another for Windows and Unix servers, says John Kogel, vice president of the systems and service management group at Candle Corp. These groups must work together and learn new terms for familiar concepts, he adds.
Since beginning its move to mainframe Linux in January 2002, WPS has cross-trained two mainframe and two Unix staffers in the combined Linux/mainframe environment. Each employee then took his knowledge back to his respective group.
Choosing the Products
The choice of Linux distribution for the mainframe matters, say users and analysts. SuSE Linux AG has the closest relationship with IBM, so about 80% of organizations running production applications on mainframe Linux use SuSE software, says Stacey Quandt, an analyst at Giga Information Group.
WPS's Lengyel, for one, chose SuSE Linux. "We like to have one focal point of support, through IBM, to support z/VM as well as the Linux environment," he says.
But SuSE's dominance may not last, Quandt says, because Red Hat improved its mainframe support relationship with IBM in the second half of 2002.
The choice of mainframe operating system also makes a big difference. Users can run Linux in native mode on IBM's older, 31-bit mainframe OS/390 operating system and can prioritize application access to resources within a partition. But IBM's latest mainframe operating system, z/OS, supports higher-throughput 64-bit processing and lets IT managers prioritize applications across multiple partitions, says Peter McCaffrey, director of product marketing for zSeries mainframes at IBM.
Users who hope to consolidate hundreds of stand-alone servers on mainframe Linux should also plan to implement IBM's z/VM, recommends Quandt. Z/VM lets users create hundreds of virtual Linux machines within each partition. Without z/VM, users are limited to 15, one for each partition. And, says Ennen, with z/VM, you don't have to bring the mainframe down to create a new Linux partition. But z/VM has a steep learning curve.
IBM also offers the Integrated Facility for Linux (IFL), a mainframe processor that runs only Linux under z/VM and costs as little as one-third as much as a similar processor used for general mainframe workloads, says Quandt. IFLs can run on IBM's Multiprise, eServer zSeries and S/390 Parallel Enterprise Servers.
Another advantage: Adding an IFL to a mainframe doesn't boost software licensing bills because IFLs aren't counted in capacity-based software pricing agreements, according to IBM.
For customers that don't have mainframes and might otherwise choose high-end Unix servers, Quandt points out that IBM offers a Linux-only z800 with three years of licensing and support at entry prices of less than $400,000, making it a cost-effective alternative to high-end Unix servers.
Mainframe Linux isn't a good fit for every application or every user. But the more you suffer from server sprawl, users and analysts say, the more you should consider it.