Linux on Mainframes: Ten Years Ago, Who Could Have Imagined?

IBM may be a big, lumbering multi-billion-dollar corporation that is slow to turn, but boy, when IBMers get imaginative, they get imaginative.

Steve Craggs of Lustratus Research recently marveled on what has become a fast-growing phenomenon: deployments of the open source Linux operating systems on mainframes. “Five or ten years ago, this sort of question would have been unthinkable, but now mainframe users are increasingly facing a choice between whether to use Linux on System z or z/OS to host new mainframe workloads.”

New Linux workloads may be the result of consolidation or initiatives such as SOA, he says.

However, IT managers and specialists appear to be divided as to how effective it is to run Linux on mainframes, versus commodity servers — and vise-versa, whether its better to stick to z/OS, the native mainframe OS. “On the one hand, long-time mainframe guys will say that z/OS has grown up with the mainframe and therefore must be the best choice. But IBM has done a lot to its version of Linux for the mainframe, and Linux bigots will be quick to point out that the license costs will be cheaper and there are strong advantages in standardizing on a portable and flexible operating system enterprise-wide.”

Linux offers flexibility, helps to drive license costs down and leverages widely available skills. The multi-system capabilities of z/OS combined with its close linkage to the System z platform offer the greatest exploitation of System z facilities. “But as always the devil is in the details,” says Craggs. “Worst of all, given the polarized nature of IT in general, the decision makers find it hard to get unbiased advice on such a divisive question.”