Extreme Slowdown using Gb Network

Michael Weber mweber at alliednational.com
Tue Mar 25 09:48:01 CST 2003


You said that "all other boxes on the network experience a crippling
slowdown" when copying large files.  Do you mean that Box C is slow
delivering data to the public network when Box A is copying files to Box
B on the private Gb network?  Or is Box C slow in talking to Box D on
the private network when the transfers are happening?

What do the network traffic lights look like on both switches?

Is there anything strange in the output of sar -n eth[01]? on both the
transfering and non-transfering systems?



>>> Seumas Macmhicean <seumas at realise.com> 03/25/03 08:49AM >>>
We are building a PE2650/PE2550/PE1650 based network usind two net
interfaces per box. One side of each box is public facing, connected
via a
100Mb NetGear Hub. The other side is private, connected via a 1Gb

We have 11 boxes connected via the private network, and it is designed
inter-box data transfer such as backups, etc. However, on copying
files (>1GB) between two boxes via the private network, all other boxes
the network experience a crippling slowdown. CPU usage is in the low
(0.02) on the other boxes at this time, so the slowdown is inside the
- is it being interrupted to death by the network interfaces?

All machines run RedHat 7.3 - one machine is soak-testing the latest
2.4.18-27 RedHat kernel whilst the others are running stock 2.4.20
(got around the tg3 lockups) - but all are affected by this slowdown.

There are no errors/overruns reported in ifconfig. The slowdown does
appear if we use the slower public network for file transfers. We are
no fancy giggerypokery either with the kernels or the network

This makes the whole concept of a Gigabit Network rather useless - can
anyone help?


  /"\----/"\                     Seumas Macmhicean RHCE 
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