Abstract: Leadership-class supercomputers, such as the ALCF Intrepid IBM Blue Gene/P system, are a challenge to design and understand. These systems consist of many design points that influence application performance. While modeling and simulating these systems is useful for identifying successful system designs, these activities are a significant challenge because it is difficult to accurately and efficiently model the interactions between system components. Parallel discrete-event simulation (PDES) tools provide a convenient way to accurately model complex interactions of these systems components with sufficient fidelity, efficiency, and fast turnaround time. In this presentation, we present a PDES model of the Intrepid PVFS storage system using the Rensselaer Optimistic Simulation System (ROSS). We validated this model using data collected on the Intrepid storage system up to 128K application cores. We show that our initial simulation results closely track observed results for the Intrepid storage system for a variety of synthetic I/O workloads.