Low Bandwidth on intercontinental connections

[Mehmet Erol Sanliturk]

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 .


Thank you very much .

Mehmet Erol Sanliturk