Multiple-Phase Collective I/O Technique for Improving Data Access Locality

This paper presents multiple-phase collective I/O, a novel collective I/O technique for distributed memory multiprocessors. Multiple-phase collective I/O is a refinement of two-phase collective I/O technique. The communication phase is structured into several steps, which progressively increase the locality of the data to be written to a file system. Besides the description of multiple-phase collective I/O, our paper addresses two additional objectives. First, the authors target to improve the efficiency of the sulphur transport Eurelian model 2 (STEM-II) application. STEM-II is an air quality model that simulates transport, chemical transformations, emission and deposition processes in a unified framework. Due to the large amount of processed data, I/O becomes a critical factor for the application performance. Multiple-phase collective I/O, considerably enhances the performance of the I/O stage in particular and, consequently, of the whole application in general. Second objective consists of evaluating and comparing the performance of multiple-phase collective I/O with that of other well known parallel I/O techniques