[Beowulf] Help with inconsistent network performance

Gerry Creager gerry.creager at tamu.edu
Wed Dec 19 09:20:00 EST 2007


One consideration is the size of the messages being exchanged.  Even 
today, small packets can markedly reduce switch performance.  RFC 2544 
compliance is not universal in the Layer 2 world.

gerry

Jon Forrest wrote:
> Brendan Moloney wrote:
>> Since it is a full duplex switched network, there should not be any 
>> collisions happening. 
> 
> I have a similar situation with a slightly larger cluster.
> At first I also thought it was a network performance
> problem. But then I ran the iftop program to watch
> the network in realtime and I saw that I wasn't
> even close to sending enough data to tax the switch.
> 
> I still don't know the cause of the problem but
> I'm pretty sure it's not cause by excessive
> network traffic. I suggest you try iftop to
> see what your program is really doing.
> 
> Cordially,

-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX 77843
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