Requirements of I/O Systems for Parallel Machines: An Application-driven Study

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I/O-intensive parallel programs have emerged as one of the leading consumers of cycles on parallel machines. This change has been driven by two trends. First, parallel scientific applications are being used to process larger datasets that do not fit in memory. Second, a large number of parallel machines are being used for non-scientific applications. Efficient execution of these applications requires high-performance I/O systems which have been designed to meet their I/O requirements. In this paper, we examine the I/O requirements for data-intensive parallel applications and the implications of these requirements for the design of I/O systems for parallel machines. We attempt to answer the following questions. First, what is the steady-state as well peak I/O rate required? Second, what spatial patterns, if any, occur in the sequence of I/O requests for individual applications? Third, what is the degree of intra-processor and inter-processor locality in I/O accesses? Fourth, does the application structure allow programmers to disclose future I/O requests to the I/O system? Fifth, what patterns, if any, exist in the sequence of inter-arrival times of I/O requests? To address these questions, we have analyzed I/O request traces for a diverse set of I/O-intensive parallel applications. This set includes seven scientific applications and four non-scientific applications. (Also cross-referenced as UMIACS-TR-97-49)