An Evaluation of the Impacts of Network Bandwidth and Dual-Core Processors on Scalability

A portion of the Cray Red Storm system at Sandia National Laboratories recently completed an upgrade of the processor and network hardware. Single-core 2.0 GHz AMD Opteron processors were replaced with dual-core 2.4 GHz AMD Opterons, while the network interface hardware was upgraded from a sustained rate of 1.1 GB/s to 2.0 GB/s (without changing the router link rates). These changes more than doubled the theoretical peak floating-point performance of the compute nodes and doubled the bandwidth performance of the network. This paper provides a analysis of the impact of this upgrade on the performance of several applications and micro-benchmarks. We show scaling results for applications out to thousands of processors and include an analysis of the impact of using dual-core processors on this system.