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Re: [OT] Network throughput



Hi!

On Fri Apr 18, 2003 at 12:22:30PM +0200, David Fokkema wrote:
> I have a laptop with a PCMCIA 10Mbit adapter connected to a 10Mbit nic on
> my server. In between is a fast ethernet switch (10/100 Mbit).
> Even as I write this mail, I'm transferring a 1Gb file from my laptop to
> my server. A simple very approximate calculation for the transfer time
> gives me:
> 
> 	10 Mbit/s ~= 1 Mb/s
> 	1Gb ~= 1000 Mb
> 
> 	=> transfer takes 1000 secs ~= 15 min.
> 
> However, this transfer takes much longer already, so I decided to try out
> ntop and I notice that the reported throughput is at only 360Kbps!
> 
> As always, there are severable possible answers, including the one that
> says that I lost all ability for handling numbers. Of course, another
> possible answer is that I made a stupid mistake.
> 
> According to ntop, its a virtually one-way flow. I'm using dd to transfer
> the image from hard drive to file which resides on a samba exported
> filesystem on my server.

10MBit is the raw traffic speed without IP Header Information. So you
NEVER can reach 10MBit. Also the quality of your NICS/Switches can
decrease network flow significanly (see http://www.fefe.de/linuxeth/
and http://www.fefe.de/linuxeth/realtek.txt). It should also be
considered that the packets have to walk through the network stacks
which should be minimal but you have to take it into account.
Also your laptops/server harddisk may decrease network throughput.
The next thing which throttles your connection significantly is the
overhead produced by samba.

So your net throughput depends on various factors and cannot be
generalized simply.

so long
Thomas

-- 
  ___    Obviously we do not want to leave zombies around.
_/___\     - W. Richard Stevens
 ( ^ >   Thomas Krennwallner <djmaecki at ull dot at>
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