libhio: Optimizing IO on Cray XC Systems With DataWarp

High performance systems are rapidly increasing in size and complexity. To keep up with the Input/Output (IO) demands of High Performance Computing (HPC) applications and to provide improved functionality, performance and cost, IO subsystems are also increasing in complexity. To help applications to utilize and exploit increased functionality and improved performance in this more complex environment, we developed a new Hierarchical IO (HIO) library: libhio. In this paper we present the motivation behind the development, the design, and features of libhio. We detail optimizations made in libhio to support checkpoint/restart IO workloads on the Trinity supercomputer, a Cray XC-40 at Los Alamos National Lab. We compare the large scale whole file read/write performance or IOR when using libhio against using POSIX when writing to Cray DataWarpTM. Keywords-libhio; DataWarp; Cray; Aries; XC40; BurstBuffer; SSD; IO