Date: Wed, 21 Nov 2012 09:20:53 -0800 From: Kevin Oberman <kob6558@gmail.com> To: Benjamin Villain <benjamin.villain@ucopia.fr> Cc: freebsd-net@freebsd.org, Marc Peters <marc@mpeters.org> Subject: Re: Low Bandwidth on intercontinental connections Message-ID: <CAN6yY1tZ=K32gRzV1DER82ksZJ6sJ-45DZAfZTX3uBvh1gvUzQ@mail.gmail.com> In-Reply-To: <50ad087d.1892cc0a.2cce.3bf2@mx.google.com> References: <50ACF62C.8000408@mpeters.org> <CAOgwaMuUuJ2%2BmKqsFVp=DyVFkfm8Et%2Brnt2iEGDO8i1Kt_kDVA@mail.gmail.com> <50ad087d.1892cc0a.2cce.3bf2@mx.google.com>
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On Wed, Nov 21, 2012 at 8:58 AM, Benjamin Villain <benjamin.villain@ucopia.fr> wrote: > I don't think this is about disk or memory leak as transfering files locally > seem to work fine. > > Can you test transferring files from (and to) your Linux boxes to (and from) > the FreeBSD servers to check that it is not a network issue inside your DCs. > > King regards, > > -- > Ben > > > Mehmet Erol Sanliturk writes: > >> On Wed, Nov 21, 2012 at 7:41 AM, Marc Peters <marc@mpeters.org> wrote: >> >> > Hi list, >> > >> > we are experiencing low throughput on interncontinental connections with >> > our FreeBSD Servers. We made several tests and are wondering, why this >> > would be. The first tests were on an IPSEC VPN between our datacenter in >> > DE and Santa Clara, CA. We are connected with two gigabit uplinks in >> > each DC. Pushing data by scp between our FreeBSD servers takes ages. >> > Starting with several MB/s it drops to 60-70KB/s: >> > >> >> >> >> ..... >> >> >> I do not have any answer to your question , but I want to share one my >> experiences . >> >> I Linux ( KDE ) I was copying a hard disk contents to another drive by >> using Dolphin . >> At the beginning it was very fast , but over time its speed reduced to a >> few kilobytes per second . >> It listed completion time left as months . >> >> I inspected why this is the case . >> >> The reason was the following : >> >> On each file it is copied , the Dolphin was producing approximately 1 >> Kilobyte memory leak . >> After copying more than one million file , all of the memory exhausted and >> it started to swap >> memory to hard disk swap space which reduced copy speed to a few kilobytes >> per second . >> >> >> I stopped the Dolphin and copied small directory groups by restarting the >> Dolphin . This cured the problem because on each exit , all of the leaked >> memory by Dolphin has been disposed ( where "Undo" item of Dolphin menu >> was >> disabled means memory is not reserved for undo ). >> >> >> Please study your data transfer software for such a possibility . It may >> not be problematic in Linux but FreeBSD version may have some trouble >> points . >> >> >> There is another possibility : Graceful degradation . >> >> http://en.wikipedia.org/wiki/Graceful_degradation >> http://en.wikipedia.org/wiki/Fail_soft >> >> A program part may produce graceful degradation over time or processed >> data >> : >> >> For example , assume a list is searched by sequentially . When list length >> grows , search times >> also grows linearly and produces a degradation although there is no any >> error in the process . >> >> You may study your system with respect to such a process . >> >> >> These are the possibilities which come to my mind . If you have not done so, I suggest you use SIFTR to capture data on what is happening in TCP. It can often tell you a great deal and is very easy to work with. Just load the kernel module and use sysctls to control it. I have used it in conjunction with tcpdump and wireshark to find performance problems. Also, for high performance on bulk data transfers over long, fat pipes, take a look at http://fasterdata.es.net. It is a detailed guide on moving data developed by the people who have to deal with the huge volumes of Large Hadron Collider data moving across the Atlantic from CERN to researchers in the US. (Note that this is not FreeBSD specific.) -- R. Kevin Oberman, Network Engineer E-mail: kob6558@gmail.com
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