Insights for exascale IO APIs from building a petascale IO API

Near the dawn of the petascale era, IO libraries had reached a stability in their function and data layout with only incremental changes being incorporated. The shift in technology, particularly the scale of parallel file systems and the number of compute processes, prompted revisiting best practices for optimal IO performance. Among other efforts like PLFS, the project that led to ADIOS, the ADaptable IO System, was motivated by both the shift in technology and the historical requirement, for optimal IO performance, to change how simulations performed IO depending on the platform. To solve both issues, the ADIOS team, along with consultation with other leading IO experts, sought to build a new IO platform based on the assumptions inherent in the petascale hardware platforms. This paper helps inform the design of future IO platforms with a discussion of lessons learned as part of the process of designing and building ADIOS.