A hybrid HPC/cloud distributed infrastructure: Coupling EC2 cloud resources with HPC clusters to run large tightly coupled multiscale applications

•We connect an EC2-cloud cluster to a university cluster located in Switzerland.•We run a distributed multiscale CFD computation over this extended infrastructure.•We evaluate and compare the distributed execution to a local execution.•We describe our experience of running parallel CFD application on hybrid platforms.•Multiscale computation on cloud requires an adjustment of CPUs power and workload.

In this paper, we report on the experimental results of running a large, tightly coupled, distributed multiscale computation over a hybrid High Performance Computing (HPC) infrastructures. We connected EC2 based cloud clusters located in USA to university clusters located in Switzerland. We ran a concurrent multiscale MPI based application on this infrastructure and measured the overhead induced by extending our HPC clusters with EC2 resources. Our results indicate that accommodating some parts of the multiscale computation on cloud resources can lead to low performance without a proper adjustment of CPUs power and workload. However, by enforcing a load-balancing strategy one can benefit from the extra Cloud resources.