Low Bandwidth on intercontinental connections

[Mehmet Erol Sanliturk]

On Wed, Nov 21, 2012 at 9:20 AM, Kevin Oberman <kob6558 at gmail.com> wrote:

> On Wed, Nov 21, 2012 at 8:58 AM, Benjamin Villain
> <benjamin.villain at 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 at 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 at gmail.com
>

A very good link .

In the above site , please see the following especially :

http://fasterdata.es.net/data-transfer-tools/say-no-to-scp/
Say No to scp
Why you should avoid scp over a WAN

and

http://fasterdata.es.net/data-transfer-tools/scp-and-sftp/
scp and sftp


Thank you very much .


Mehmet Erol Sanliturk