Sun MPI Interprocess Traffic

Parallel programs use Sun MPI to move data between processes as the program runs. If the running program is spread across multiple cluster nodes, then the program generates network traffic.

Sun MPI will use the network that the CRE instructs it to use, which can be set by the system administrator. In general, the CRE instructs Sun MPI to use the fastest network available so that message-passing programs obtain the best possible performance.

If the cluster has only one network, then message-passing traffic will share bandwidth with administrative and CRE functions. This will result in performance degradation for all types of traffic, especially if one of the applications is performing significant amounts of data transfer, as message-passing applications often do. The administrator should understand the communication requirements associated with the types of applications to be run on the Sun HPC cluster in order to decide whether the amount and frequency of application-generated traffic warrants the use of a second, dedicated network for parallel application network traffic. In general, a second network will significantly assist overall performance.