[Gluster-users] help, glusterfs test caused very high tcp segment retransmission rate (Collin Douglas)

[Collin Douglas]

I'll be interested to hear how this works for you.  THanks for the update.

-Collin

Dai, Manhong wrote:
>
> Hi Collin,
>
>   Thanks a lot for your help. The interconnect is Gigabit Ethernet.
>
>   I am guessing that it is caused by the router. Computing nodes that 
> connect to this router always retransmit 5% of segments under heavy 
> load. My test on other router has lower ratio, around 0.3%. I am about 
> to replace the router and perform another test.
>
>   Anyway this problem is not related to glusterfs at all. Although I 
> do have another question that is about glusterfs, which I will send in 
> a separated email.
>
> Best,
> Manhong
>
> Date: Mon, 25 Aug 2008 08:41:25 -0500
> From: Collin Douglas <cbd at adfitech.com>
> Subject: Re: [Gluster-users] help, glusterfs test caused very high tcp
>         segment retransmission rate
> Cc: gluster-users at gluster.org
> Message-ID: <48B2B685.2050603 at adfitech.com>
> Content-Type: text/plain; charset="ISO-8859-1"
>
> -----BEGIN PGP SIGNED MESSAGE-----
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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
>
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>
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