The network benchmarks are based on NetPIPE. Each node comes with two gigabit network interfaces, which unfortunately, have very different performances, although they are both based on RealTek chipsets. The graphs below compare the on-board NIC (RTL8168B, green line) with the PCI NIC (RTL8169sb, orange line) with respect to throughput vs. message size. The PCI NIC has significantly lower throughput with messages longer than 64K, but appears to perform better with shorter messages. The cross-over point of 64K should be telling me something (about TCP buffers ?), but I haven't figured-out what. The apparent 'steps' in these graphs are due to NetPipe's triply-repeated measurements for each message size.

The latency results (shown below) are very similar for the two cards, with an average value of 23μs.