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A Decade of SUSE Linux Enterprise Server on the IBM Mainframe

Written by Bill Tobey

May 17, 2010 marks the tenth anniversary of commercially distributed, fully supported Linux on the IBM mainframe.. On that day in 2000, SuSE (later SUSE LINUX AG, acquired by Novell in early 2004) announced the first availability of SUSE Linux Enterprise Server for S/390. An eventful decade later, it’s difficult to recall just how improbable this development seemed at the time, but it’s worth pausing to reconsider how Linux reconnected the diverging worlds of mainframe and distributed computing, and the impact of that development on the past and future evolution of enterprise IT.

The Last Closed Platform

By the late 1990s IBM was engaging the open source software community on multiple fronts. Linux was running on its Power and x86 systems, the company had joined the Apache Project, and researchers across the organization were contributing time and code—sometimes officially, sometimes independently—to assorted community efforts. But open source remained an open issue in some areas, and the company’s crown jewel, the System 390, was still proudly and pristinely proprietary. Of course the idea of any non-native OS running on an IBM mainframe was so controversial that an internal project to port Linux for the S/390, based in Böblingen, Germany, was carefully kept secret from the rest of the organization.

That began to change in December 1998 with a top-to-bottom review of IBM’s open source strategy. The verdict: open source innovation would ultimately drive growth for IBM. As successful Linux applications evolved into mission-critical business services, those workloads would inevitably migrate onto mission-critical platforms, including the mainframe. In December 1999, the Böblingen team released its work to the community: a collection of extensions and patches providing a functional SMP kernel, console, Glibc, gcc, binutils and gdb patches. IBM wouldn’t release a distribution of its own, but the invitation to existing distributors couldn’t be clearer. The ultimate closed environment was open to open source.

First to the Mainframe Party: SUSE Linux Enterprise Server

SuSE was the first established distributor to respond. A SuSE team approached IBM, offering a proof of concept distribution in exchange for an architectural orientation to the mainframe environment and a reference system for development. With the system created at Marist College from IBM patches running on a borrowed Multiprise 3000, they used the SuSE AutoBuild system to create packages. “After the first weekend we had 400 packages,” recalls Marcus Kraft, product manager for SUSE Linux Enterprise Server for System z . The team also adapted YaST and edited the package selection for a mainframe distribution.

But the technical obstacles, while large, did not compare to the business challenge of adapting SuSE’s packaged software business model for the low-volume, service-intensive mainframe market. “Enterprise customers and ISVs needed a stable code base to build solutions on,” Kraft says, “but Linux was evolving very quickly. So we decided to basically freeze the code base, maintain it to ensure hardware and software compatibility, then offer subscription-based services on top of that—and customers resonated with this approach.”

SUSE Linux Enterprise Server for S/390 was born.

The First True Cross-platform Linux

The release of SUSE Linux Enterprise Server for S/390 completed the first true cross-platform Linux offering and introduced Linux to the platform farthest from its x86 roots. The IBM System 390 was the architectural opposite of contemporary PC-based servers. Its massive processing resources were perfectly balanced with memory and I/O subsystems to consistently optimize CPU use. Distributed processing capacity, primarily in the form of dedicated I/O channel processors, limited subsystem overhead on CPUs. Thorough attention to hardware component and system design and painstaking elimination of single points of failure in hardware and microcode provided reliable, available and serviceable functioning at unmatched levels. Virtualization technologies with 30 years of operational refinement allowed efficient logical partitioning of physical resources and complete isolation of multiple operating environments. Perhaps most uniquely, System 390 preserved an unbroken 40-year history of backward binary compatibility, thus preserving customer investments and commitment to the platform.

A Platform on the Move

But the mainframe was also evolving rapidly under a changing business environment characterized by new workloads, increasing cost pressure and the disruptive proliferation of distributed computing systems. Soon after SuSE released its Linux for S/390, IBM introduced the eServer zSeries 900, the first mainframe purpose-built for e-business. The new release included z/OS, a new 64-bit operating system, and z/VM, a new hypervisor capable of running hundreds or even thousands of virtual machines on a single physical system.

The current state of mainframe arts is the IBM System z10 Enterprise Class, with up to 64 configurable 4.4 GHz processor cores, 1.5 TB of memory, a new InfiniBand host bus with a link data rate of 6 GB/s each (maximal number per system is 48, in total up to 288GB/s of aggregate I/O throughput), and a broad range of available specialty engines including the Integrated Facility for Linux (IFL). A variety of capacity on demand (CoD) options give the System z10 temporary or permanent capacity scaling on the fly. This is a platform specifically designed for efficient, large-scale consolidation of distributed workloads, and Linux support is intrinsic to its mission.

A Decade of Co-evolution

Synchronizing SUSE Linux Enterprise Server development with mainframe platform innovation has forged an enduring partnership between Novell and IBM. When IBM introduced 64-bit adaptations for Linux for System z, SuSE developers proposed the File Hierarchy Standard changes necessary to support the larger address space and co-existence of 32-bit and 64-bit applications within the same Linux instance, preserving ease of migration onto the new system for existing ISV applications. As the mainframe microarchitecture has evolved, SUSE Linux Enterprise Server has consistently been the first distribution to support new instructions. Novell has invested heavily in support capabilities to serve IBM’s global customer base, and in ISV outreach programs to certify more than 1,000 third-party applications for SUSE Linux Enterprise Server for System z.

Novell has also consistently driven innovation to simplify life for customers who choose to run Linux workloads on their IBM mainframes. One example is the SUSE Linux Enterprise Server Starter System for System z, a complete pre-built installation server that can be deployed in a mainframe environment to streamline and simplify subsequent installation of virtual Linux servers.

For Novell, the return on this investment has been a dominant position in the mainframe Linux market space with more than 80 percent share of Linux on mainframe deployments and fully 75 percent of the SAP on Linux installations. For customers, the return is a proven OS platform for Linux workload migration to the mainframe that is fully supported by IBM worldwide.

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