mini-cluster network delays

Felix Rauch rauch at
Thu Jan 18 00:55:56 PST 2001

On Wed, 17 Jan 2001, Kris Thielemans wrote:
> I have some delays in network access between different machines in our
> mini-cluster. This is not really a beowulf (yet), but I hope somebody can
> help me how to find out what's going wrong.
> Our cluster has 4 identical Linux PCs (SuSE 6.3), each of them with  100Mbit
> Ethernet connection to an Ethernet switch (and from the switch also a 10Mbit
> to the 'outside').

Did you check that your switch and your nodes agree on the
duplex-setting for the network? Sometimes it happens that the NIC uses
half-duplex while the switch uses full-duplex connections (or the
other way around). This could cause network problems. The reason is
that the auto-negotiation doesn't always work, so it should help to
set your NIC to a fixed setting, e.g. full-duplex.

- Felix
Felix Rauch                      | Email: rauch at
Institute for Computer Systems   | Homepage:
ETH Zentrum / RZ H18             | Phone: ++41 1 632 7489
CH - 8092 Zuerich / Switzerland  | Fax:   ++41 1 632 1307

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