The aim of this talk is to present the design and implementation of a new file system independent collective I/O optimization based on file views: view-based collective I/O. View-based collective I/O has been implemented and evaluated inside the ROMIO implementation of the MPI-IO standard. The evaluation section shows that view-based I/O outperforms the original two-phase collective I/O from ROMIO in most of the cases for three well-known parallel I/O benchmarks. This is especially due to a smaller cost of scatter/gather operations, a reduction of the metadata overhead, and a smaller number of collective communication and synchronization primitives used in the implementation.

In addition, I will present an implementation of the MPI-IO interface for GPFS inside ROMIO distribution. The experimental section presents a performance comparison among three collective I/O implementations: two-phase I/O, view-based I/O, and a GPFS specific collective I/O implementation based on data shipping. The measurements show that data shipping-based collective I/O performs better for writing, while view-based I/O for reading.