Gluster users - Aug 2008 - help, glusterfs test caused very high tcp segment retransmission rate

Hi,

  
   I found the aggregated IO speed is only about 100MB/s on 4 Giga-bit Brick.
This test is done over 12 computing nodes with command dd if=/dev/zero of=bar
bs=1048576 count=20480. Because our brick has very fast local IO speed, the
problem could be network.


  Then I found computing nodes got too many retransmited segments during test
according to netstat -st. The retransmission ratio is about 5%, but brick node
has a normally low transmission rate.


  Could some shed some light?

Best,
Manhong
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This sounds a lot like a physical layer issue -- most notably a 
speed/duplex issue.  Any time I've seen a large number of retransmits 
occur during heavy load, this is what I suspect.

That said, I don't know what type of interconnect you're using.  Tell us
more about your configuration.

- -Collin

Dai, Manhong wrote:
>
>
> Hi,
>
>  
>    I found the aggregated IO speed is only about 100MB/s on 4 Giga-bit 
> Brick. This test is done over 12 computing nodes with command dd 
> if=/dev/zero of=bar bs=1048576 count=20480. Because our brick has very 
> fast local IO speed, the problem could be network.
>
>
>   Then I found computing nodes got too many retransmited segments 
> during test according to netstat -st. The retransmission ratio is 
> about 5%, but brick node has a normally low transmission rate.
>
>
>   Could some shed some light?
>
> Best,
> Manhong
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Gluster-users mailing list
> Gluster-users at gluster.org
> http://zresearch.com/cgi-bin/mailman/listinfo/gluster-users
>   
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