Extreme Slowdown using Gb Network

Seumas Macmhicean seumas at realise.com
Tue Mar 25 08:48:00 CST 2003

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 NetGear

We have 11 boxes connected via the private network, and it is designed for
inter-box data transfer such as backups, etc. However, on copying large
files (>1GB) between two boxes via the private network, all other boxes on
the network experience a crippling slowdown. CPU usage is in the low zeroes
(0.02) on the other boxes at this time, so the slowdown is inside the kernel
- 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 kernels
(got around the tg3 lockups) - but all are affected by this slowdown.

There are no errors/overruns reported in ifconfig. The slowdown does not
appear if we use the slower public network for file transfers. We are using
no fancy giggerypokery either with the kernels or the network interfaces.

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


  /"\----/"\                     Seumas Macmhicean RHCE 
  \/ o  o \/                     Senior Systems Engineer
   |  qp  |    
    \ /\ /    Realise Ltd, Quay House, 142 Commercial Street, Edinburgh 
    [[><]]    http://www.realise.com/                Tel: 0131-476 6000

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