A library called HIO has been developed for largescale multi-physics simulations, based on the UDM library [10]. The goal of the library is to provide sustainable, interoperable, efficient, scalable, and convenient tools for parallel 10 and data management for high-level data structures in applications, and to provide tools for the connection between applications. The high-level data structures include one-and multi-dimensional arrays, structured meshes, unstructured meshes, and the meshes generated through adaptive mesh refinement. The 10 mechanism can be collective and non-collective. The data objects suitable for the library could be either large or small data sets. Even for small data sets, the 10 performance is close to one of MPI-IO performance.