Impact of Data Placement on Parallel I/O Systems\Lambda

Abstract The I/O performance of several concurrent exter-nal merge jobs sharing a parallel I/O system is studied. The placement of the runs is found to have a sig-nificant impact on performance. Placements leading to serialization among jobs were identified and ana-lyzed, and solutions discussed. Contrary to the behavior of a single merge, increasing the buffer size in thissituation may actually degrade performance.