Efficient Support for MPI-I/O Atomicity Based on Versioning

We consider the challenge of building data management systems that meet an important requirement of today's data-intensive HPC applications: to provide a high I/O throughput while supporting highly concurrent data accesses. In this context, many applications rely on MPI-I/O and require atomic, non-contiguous I/O operations that concurrently access shared data. In most existing implementations, the atomicity requirement is implemented through locking-based schemes, which have proven inefficient, especially for non-contiguous I/O. We claim that using a versioning-enabled storage back-end has the potential to avoid the expensive synchronization induced by locking-based schemes. We describe a prototype implementation on top of ROMIO, and report on promising experimental results with standard MPI-I/O benchmarks specifically designed to evaluate the performance of non-contiguous, overlapped I/O accesses under MPI atomicity guarantees.