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: 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----- Hash: SHA256 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://zresearch.com/pipermail/gluster-users/attachments/20080825/2099f803/attachment.htm
