  We have seen an increase in the heterogeneity of storage technologies
potentially available to scientific applications, such as burst buffers,
managed cloud parallel file systems (PFS), and object stores. However, those
applications cannot easily utilize those technologies, because they are
designed for traditional HPC systems that offer very high remote storage and
network bandwidth. We present iFast, a new distributed host-side logging
approach to transparently accelerating scientific applications. iFast has a
strong emphasis on deployability, supporting unmodified MPI applications with
unmodified MPI implementations while preserving the crash consistency
semantics. We evaluate iFast on traditional HPC, cloud HPC, local cluster, and
a hybrid of both, using three scientific applications. iFast reduces end-to-end
execution time by 13-26% for popular scientific applications on the cloud. We
show for the first time, how an application on a recent production HPC system
can write data to S3 storage through fully fledged MPI-IO, in a readily
shareable format.
