Enabling Transparent Asynchronous I/O using Background Threads

Abstract

With scientific applications moving toward exascale levels, an increasing amount of data is being produced and analyzed. Providing efficient data access is crucial to the productivity of the scientific discovery process. Compared to improvements in CPU and network speeds, I/O performance lags far behind, such that moving data across the storage hierarchy can take longer than data generation or analysis. To alleviate this I/O bottleneck, asynchronous read and write operations have been provided by the POSIX and MPI-I/O interfaces and can overlap I/O operations with computation, and thus hide I/O latency. However, these standards lack support for non-data operations such as file open, stat, and close, and their read and write operations require users to both manually manage data dependencies and use low-level byte offsets. This requires significant effort and expertise for applications to utilize. To overcome these issues, we present an asynchronous I/O framework that provides support for all I/O operations and manages data dependencies transparently and automatically. Our prototype asynchronous I/O implementation as an HDF5 VOL connector demonstrates the effectiveness of hiding the I/O cost from the application with low overhead and easy-to-use programming interface.