Looking for advice on a gigabit networking problem

[Howard Wilkinson]

This may not be right forum to ask this question but I am hoping some 
Fedora buffs will know the right place for me to go with this.

I have a network built around some Cisco switches. There is a 3550-12T 
and a pair of 2950-48's connected via gigabit links to this switch. I 
have 7 server boxes connected onto the 3550 via Intel E1000 cards. These 
servers also have 100 Mbps links to the 2950's over e100 on board nic's. 
I have the 3 nic's on each server set up under a bonding driver in 
active backup mode with the gigbit nic as the active master and the 100 
Mbps nic as the passive backups. Everything functions as expected with 
fail over on link failure being 100% transparent ( 8-) ) EXCEPT the 
bandwidth available down the gig links server to server is at best 288 
Mbps! The bond runs a native (untagged VLAN) and a tagged VLAN offering 
on 2 separate networks. The machines are Intel SRMK4 running dual 
1GigaHz Xeon's vintage 2000/2001 with 4GB of memory and the latest stock 
Fedora 9 PAE kernels.

I have set up iperf tests and thumped as hard as I can on the E1000 
tuning parameters and this is the best I can achieve. Now what I want to 
know is should I be able to do better with this set up. I am wondering 
if I am hitting limits on the PCI bus, the switching capability of the 
3550 or just that the E1000's can't really provide full bandwidth 
without using jumbo frames (which are not available as the bond driver 
stops this).

Does anybody have any ideas, or pointers to likely solutions?

Regards, Howard