Diagnosing a slow network

[gaf at blu.org (Jerry Feldman)]

On Mon, 9 Aug 2004 23:50:11 +0100
heidi at midnighthax.com wrote:

> I'm trying to work out why copying a file across my network is so
> slow. There are four Linux boxes connected to a 100Mb switch, and
> copying a 300Mb from one system to another runs at 500K/second. The
> systems aren't busy, so it could be a network card problem, a hard
> disk being slow, or - what? I'm using scp to do the copy, so there
> will be some overhead with encryption, but 500K/sec is way too slow.
> Any ideas on how to troubleshoot this?
While all the other solutions posed make sense, I have not seen anyone
propose the use of diagnostic software such as netperf, ttcp. You can
use these utilities to test the raw network performance between the
systems. 
netperf: http://www.netperf.org/netperf/NetperfPage.html
ttcp:    http://www.pcausa.com/Utilities/pcattcp.htm

My old laptop did not have a built-in and I bought a PCMCIA card that
supported 10/100. I then ran one of these benchmarks and found that I
was not getting close to 100Mbps. I returned the card for a cardbus
card. Also, as David mentioned, your network cards should be configured
for full-duplex. Most will automatically come up with full-duplex, but I
have seen some cards that somehow get stuck in half-duplex. 



-- 
Jerry Feldman <gaf at blu.org>
Boston Linux and Unix user group
http://www.blu.org PGP key id:C5061EA9
PGP Key fingerprint:053C 73EC 3AC1 5C44 3E14 9245 FB00 3ED5 C506 1EA9
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