Hint Controlled Distribution with Parallel File Systems

The performance of scientific parallel programs with high file-I/O-activity running on top of cluster computers strongly depends on the qualitative and quantitative characteristics of the requested I/O-accesses. It also depends on the corresponding mechanisms and policies being used at the parallel file system level. This paper presents the motivation and design of a set of MPI-IO-hints. These hints are used to select the distribution function with which a parallel file system manipulates an opened file. The implementation of a new physical distribution function called varstrip_dist is also presented in this article. This function is proposed based upon spatial characteristics presented by I/O-access patterns observed at the application level.