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Home > Data Center News > Linux on the IBM mainframe: When is it the right choice? |
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The applications are probably the No. 1 factor and, in particular, how many Linux applications you have, according to IBM, analysts and mainframe users. If you have only a single Linux server running one application, it isn't worth buying an Integrated Facility for Linux (IFL), the specialty mainframe processor that will run you about $100,000, depending on your mainframe. But if you have thousands, hundreds or even dozens of Linux servers, you might want to consider the mainframe. That's because all your Linux servers can run as virtual instances on top of z/VM, the mainframe's virtualization operating system, on the IFL engine. John Phelps, a research vice president of servers at research firm Gartner Inc. who recently wrote a report exploring the argument for putting Linux on the mainframe, said that "if you're talking 20 to 30 applications, you're probably not looking at the mainframe. If you keep going up, it has great consolidation capability."
In a similar vein, Brad Day, an analyst at Forrester Research Inc., said that the sweet spot for breaking even on the z9 Business Class – a smaller mainframe that starts at about $100,000 – is 25 to 30 Linux instances. Mainframe attractive consolidation target That consolidation onto five IFL engines reduced the Quebec government's overall hardware and software licensing costs. Though the cost of the mainframe hardware was about the same as buying Unix server hardware, the agency estimated that it saved $800,000 in licensing costs in the first year alone. Oracle licenses are based on the number of processors used, so the agency saved money by being able to host several Oracle instances on each IFL specialty processor. David Kreuter, president of Ontario-based VM Resources Ltd., which consulted on the project, said the only other hurdle was training some staff to learn Linux and z/VM. "We worked out a lot of pressure points by spending a good deal of time developing a very solid architecture," he said. "The savings and license reduction was what was attractive." Supermarket chain Hannaford Bros. is also consolidating Linux instances on its existing mainframe. Right now CIO Bill Homa said the company has about 70 Linux instances on big iron, and setting up a new one is easier than configuring a physical Linux server. "You can set up a virtual Linux server on the mainframe in about a minute, just with a few commands," he said. "In fact, our corporate Web server for our Internet is moving to the mainframe tomorrow from a couple servers, and that's not a very difficult move." These consolidations have also helped both organizations reduce their data center footprint, allowing Hannaford to save on power and cooling costs. That's something that IBM has touted for its mainframe. Earlier this month, IBM announced that over the past two months it had measured the energy efficiency of about 1,000 mainframes and found that they were much more efficient than a scale-out x86 infrastructure. Workload matters – or does it? But Charlie Burns, a vice president at Westport, Conn.-based research firm Saugatech Technology Inc., didn't necessarily agree. If the person administering the mainframe knows how to manage it so the research application doesn't sabotage the server's CPU, then it's possible to put those workloads on big iron. "What you need to do is make sure that you don't allow that extraneous workload to consume the entire mainframe," he said. "That's a matter of setting priorities and workload objectives, and the tools exist to do that quite handily." Mainframe-compatible applications If you're writing your own Linux applications in-house, adjusting them from x86 Linux to mainframe Linux shouldn't be a big hassle. "If it's not supported on Linux on the mainframe, people aren't going to run it there," Phelps said. "So are you developing your own Linux applications, or are you depending on ISVs?" Having a mainframe helps "The mainframe is an environment that many people aren't even used to running," Phelps said. "One of the things it depends on is if you have experience on it already. If I already have a mainframe, putting an IFL on there is not that big a deal." Even for those companies that do have a mainframe, transitioning can be difficult from a personnel perspective. At the province of Quebec, staff accustomed to Unix environments like AIX and Solaris had to be re-trained in z/VM and Linux. Kreuter said most of the issues involved "improving the skills of the staff to accept new z/VM and Linux technology." In addition to learning new operating systems, staffers need to know how to manage a virtualized environment. Saugatech's Burns said that some things you might do to increase the performance of a physical Linux server could harm a virtual Linux server on z/VM. IT staff, for example, might be accustomed to adding memory to a server to increase performance. But if you add virtual memory to a virtual server, you could affect other virtual servers running on the same physical host. "You have to be more broad in your thinking in terms of 'How do I manage, how do I run a virtualized infrastructure?'" Let us know what you think about the story; email Mark Fontecchio, News Writer. You can also check out our Server Specs blog.
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