Thanks everyone for your kind answers.
> The Asante GX5-2400W does not support jumbo frames. You could try
> frame sizes above 1500 (in say, increments of 500) to find a maximum,
> but it's probably very close to 1500.
!!!! It is true I had not checked !!!!
(There was probably a misunderstanding between me and my provider...)
I am sorry for bothering you with this question...
> My personal experience with MPI over ethernet is that jumbo frames are
> usually not more important than switch performance. If you test
> transfer rates on an idle machine, you find that the speed is about
> the same whether you use an MTU of 1500 or an MTU of 9000. But, the
> transfer itself can easily use 30% of the processor's time (this is
> for a 2.0GHz Opteron, and probably G5 as well). If the sends are
> non-blocking, then the available processing power is down 30% during
> the communication time. Jumbo frames should chop it to 15% on average.
> So when doing CPU intensive calcs which are also communications
> intensive, the jumbo frames "may" speed things up a few percent.
>
> You should look at trunking. It probably won't save CPU usage, but it
> should halve transmittion times.
...but I learned things !
and I'll consider all your suggestions.
Thanks once more,
--
Christian
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