On Apr 6, 2010, at 19:01 , David Mathog wrote: > What's bothering me though is that both D-link and Netgear claim the > same top forwarding rate as the more expensive switches, at 48 Gbps. > Giving them the benefit of the doubt, that they are not intentionally > misrepresenting the speed of these units, perhaps there is some other > variable in play which degrades their performance more than the other > switches?
You should check that XON/XOFF (PAUSE protocol) is enabled in _both_ directions by means of ethtool. DIfferent switches have different defaults. Sometimes, enabling XON/XOFF has a dramatic positive effect on packet loss. > This is another one of those cases where having a benchmark would be > enormously helpful. I tend to use an MPI which can run over TCP/IP and run a naive all-to-all benchmark, changing payload sizes and number of active MPI processes per node. As a side note, Linux has in the order of ten different congestion protocols, but none of them seems useful in an HPC environment, when you're exposed to packet loss. Håkon _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
