Understanding the characteristic I/O behavior of scientific applications is an integral part of the research and development efforts for the improvement of high performance I/O systems. This study focuses on application level I/O behavior with respect to both static and dynamic characteristics. We observed the San Diego Supercomputer Center's Cray C90 workload and isolated the most I/O intensive applications. The combination of a low-level description of physical resource usage and the high-level functional composition of applications and scientific disciplines for this set reveals the major sources of I/O demand in the workload. We selected two applications from the I/O intensive set and performed a detailed analysis of their dynamic I/O behavior. These applications exhibited a high degree of regularity in their I/O activity over time and their characteristic I/O behaviors can be precisely described by one and two, respectively, recurring sequences of data accesses and computation periods.>

Past research on high performance computers for scientific applications has concentrated on CPU speed and exploitation of parallelism, but has, until very recently, neglected 1/0 considerations.This paper presents a study of the production workload at the San Diego Supercomputer Centerfrom an 110 requirements and characteristics perspective.Results of our analyses support our hypothesis that a significant proportion of 110 intensive, long running, frequently executed scientific applications have predictable 110 requirements.Pemnission to copy Wbcut fee all or pm of this material is granted, provided that th copes am nci made or distributed for &red commercial advantage, the ACM copyright mice and the title of the Wblication and its date appear, and notice is given that ccpying is by penmsmon of the Association for Cbm@ng Mec+mte~.To copy othemvise, or to repubhsh, reqlires a fee andlar specWc psrtnission.