  This short paper deals with parallel scientific applications using
non-blocking and periodic coordinated checkpointing to enforce resilience. We
provide a model and detailed formulas for total execution time and consumed
energy. We characterize the optimal period for both objectives, and we assess
the range of time/energy trade-offs to be made by instantiating the model with
a set of realistic scenarios for Exascale systems. We give a particular
emphasis to I/O transfers, because the relative cost of communication is
expected to dramatically increase, both in terms of latency and consumed
energy, for future Exascale platforms.
