Impact of topology and link aggregation on a PC cluster with Ethernet

In addition to its use in local area networks, Ethernet has been used for connecting hosts in the area of high-performance computing. Here, we investigated the impact of topology and link aggregation on a large-scale PC cluster with Ethernet. Ethernet topology that allows loops and its routing can be implemented by the VLAN routing method without creating broadcast storms. To simplify the system configuration without modifying system software, the VLAN tag is added to a frame at switches in our implementation of topologies. Each host creates VLAN interfaces that have different local network addresses on a physical interface, so that a switch learns the MAC addresses of hosts in a PC cluster by broadcast. Evaluation results showed that the performance characteristics of an eight-switch network are comparable to those of an ideal 1-switch (full crossbar) network in the execution of high-performance LINPACK benchmark (HPL) on a 225-host PC cluster. On the other hand, evaluation results using NAS parallel benchmarks indicated that topologies achieved by the proposed methodology showed performance improvements of up to about 650% as compared to the simple tree topology. These results indicate that topology and link aggregation have marked impacts and commodity switches can be used instead of expensive and high functional switches.