Channel bonding performance problem

[Hao He]

Hi there.

I just finished some channel bonding test with 2 Dual-3C905-NIC PCs. 
But the network performance is only a little bit higher than single NIC case.
I don't know why. Following are the details:

Node configuration:
Intel Pentium III
Dual 3C905 NIC
Redhat 7.1 (2.4.2)

When Linux installed, I created bond0 and modified modules.conf and ifcfg-eth0, ifcfg-eth1, ifcfg-bond0
according the mini-Howto.
After rebooting the system, I saw that channel bonding was sucessful since by running ifconfig, 
I found bond0, eth0, eth1 had same IP address and MAC address.

Then I installed netperf 2.1. I have to removed most default arguments to compile it on my system.

When I just did local test by netperf, the result looked good. The speed was more than 700Mbps, doubled
from before. However, when I tested the network performance between the 2 nodes, I found the improvement 
is quite limited, say, only about 10% (from 90Mbps to 100Mbps).

I checked the system by running ifconfig. It seems the bonding worked well because the RX, TX data of the 2 NICs 
are almost equal which means the communication task are assigned averagely to the 2 cards.

Then I tried to FTP a big file( 115MB) between the two nodes. This time I got a average speed of about 9.2MB/s.
Seems this speed is doubled then before. So I am confused.

I don't know why and how to solve this problem.
Any suggestion and help from you will be highly appreciated.

Thank you!

Best regards,
Hao He