Comprehensive Scientific Support

NERSC’s comprehensive scientific support ranges from everyday high-quality operations and client services to direct collaboration with scientists to solve unique computational and data management problems. Whether the challenge involves system software, networks, algorithms, application codes, or visualization tools, NERSC’s goal is always the same—to help make the DOE scientific community more productive.

Making Systems Productive for Science

NERSC users in 2002 saw significant improvements in job turnaround time thanks to the work of the Queue Committee, made up of NERSC Users Group volunteers and NERSC staff. Based on the committee’s recommendations, NERSC improved turnaround time for interactive and debug jobs during prime time by setting aside 5% of the Seaborg compute nodes for these jobs from 5:00 a.m. to 6:00 p.m. Pacific time, Monday through Friday. To improve fairness, we also implemented priority aging for regular class jobs—regular jobs in the queue for more than 36 hours will not be preempted by new premium jobs. In addition, we provided a new regular_long class with a connection time of up to 24 hours for jobs using 32 nodes or less. A special mechanism was implemented to allow science-of-scale projects to run continuously to use their large allocations.

The NERSC networking team continues working with users at remote sites to improve end-to-end network performance. During the past year, the data transfer rate to and from Princeton Plasma Physics Laboratory was increased from 700 KB/s to 2 MB/s. We achieved a 7x network performance improvement with Fermilab, a 5x improvement with the State University of New York at Stonybrook, and a 2.5x improvement with Brookhaven National Laboratory. Other networking achievements included implementation of an Access Grid node for multicast videoconferencing, and installation of a spam filter on NERSC mail servers. An ESnet link upgrade to OC-48 (2.4 GB/s) is expected to be in production early in 2003.

	Figure 1   The PDSF Team—Steve Chan, Shane Canon, Cary Whitney, Iwona Sakrejda, and Tom Langley—helped the SNO collaboration analyze data that answered longstanding questions about solar neutrinos. (Steve now works in NERSC’s Networking and Security Group.)

NERSC’s PDSF cluster system is used by several large high energy and nuclear physics collaborations for data analysis and simulations, and NERSC staff work closely with these groups to support their efforts and to improve the PDSF system (Figure 1). When data from the Sudbury Neutrino Observatory (SNO) were analyzed on the PDSF, the results revealed that solar neutrinos do have mass and transform from one “flavor” to another in transit from the core of the sun to the earth. Data from the KamLAND experiment, also analyzed on the PDSF, confirmed these results for anti-neutrinos generated by nuclear reactors.

One of the largest users of the PDSF and NERSC’s HPSS archive is the Solenoidal Tracker at RHIC (STAR) collaboration, which transfers approximately 1 TB of data per week from Brookhaven National Laboratory to NERSC, with more than 65 TB stored in our HPSS archive to date. Results of the STAR experiment have been analyzed on the PDSF and published in a dozen journal articles, with more to come. Because STAR is actively involved in the Particle Physics Data Grid, PDSF was the first production machine at NERSC to offer Grid services, including various versions of Globus.

Figure 2   Harsh Anand Passi installs the latest climate modeling codes on NERSC systems and helps researchers use them effectively.

Harsh Anand Passi, a member of NERSC’s consulting staff, provides key support for climate modeling researchers (Figure 2). She spearheaded one of the first parallel implementations of the netCDF library, provides initial visualization support for climate models, and has been the technical leader for installing several climate codes on NERSC systems, most recently the Community Climate System Model (CCSM2). She created methods that allow researchers to modify CCSM manageably, and developed documentation on the code for the NERSC Web site. As a result of her work, NERSC is the only site besides the National Center for Atmospheric Research that runs a fully supported CCSM2.