The scale of Leadership Class Systems presents unique challenges to the features and performance of operating system services. This paper reports results of comprehensive evaluations of two Light Weight Operating Systems (LWOS), Cray's Catamount Virtual Node (CVN) and Linux Environment (CLE) operating systems, on the exact same large-scale hardware. The evaluation was carried out over a 5-month period on NERSC's 19,480 core Cray XT-4, Franklin, using a comprehensive evaluation method that spans Performance, Effectiveness, Reliability, Consistency and Usability criteria for all major subsystems and features. The paper presents the results of the comparison between CVN and CLE, evaluates their relative strengths, and reports observations regarding the world's largest Cray XT-4 as well.

This is the sixth self-assessment of the systems and services provided by the U.S. Department of Energy's National Energy Research Scientific Computing Center, describing many of the efforts of the NERSC staff to support advanced computing for scientific discovery. The report is organized along the 10 goals set by our staff and outlines how we are working to meet those goals. Our staff applies experience and expertise to provide world-class systems and unparalleled services for NERSC users. At the same time, members of our organization are leading contributors to advancing the field of high-performance computing through conference presentations, published papers, collaborations with scientific researchers and through regular meetings with members of similar institutions. In the fast-moving realm of high-performance computing, adopting the latest technology while reliably delivering critical resources can be a challenge, but we believe that this self-assessment demonstrates that NERSC continues to excel on both counts.

Once a year, the SC conferences present a unique opportunity to create and build one of the most complex and highest performance networks in the world. At SC2000, large-scale and complex local and wide area networking connections were demonstrated, including large-scale distributed applications running on different architectures. This project was designed to use the unique opportunity presented at SC2000 to create a testbed network environment and then use that network to demonstrate and evaluate high performance computational and communication applications. This testbed was designed to incorporate many interoperable systems and services and was designed for measurement from the very beginning. The end results were key insights into how to use novel, high performance networking technologies and to accumulate measurements that will give insights into the networks of the future.