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I have two new dell servers, both pretty close to the same hardware. One has RHEL6 installed and one has CentOS 6 installed.

I have the machines configured identically from a network-scripts, modprobe.d and sysctl.conf settings (did a diff on sysctl.conf to confirm).

All four physical ports are on a Cisco 3750X Stacked Switch and are configured identically except for each server pair has their own channel.

With the command dd if=/dev/zero bs=4k count=262140 | ssh {host} 'cat > /dev/null'

I get roughly 100MB/s from the RHEL6 box, but only about 35MB/s on the CentOS6 box.

Any ideas?

I can post the various configs but there are a lot of them, don't want to have a huge post unnecessarily...

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I'm chalking this up to less effective hardware, the slower server is using bnx2 module while the other server is using tg3 (with an upgraded broadcom card) but I would not have expected such poor performance from the stock GigE ports, can hardly claim to be GigE if they're performing at 35MB/s. – Clint Priest Jun 14 '13 at 21:43
Have you taken a look at your /proc/net/bonding/bond0 file? The slave queue id's should be the same. I remember having an issue in the past that was similar to yours and the culprit was mismatched values in /proc/net/bonding/bond0 – pullsumo Jun 19 '13 at 21:57
Just as a followup, I did try RHEL6 on the lower-end machine running CentOS 6 that was slower, RHEL6 performed no better. I have not had a chance to check these other suggestions but will soon. – Clint Priest Jun 30 '13 at 13:51

Are the SSH configurations and CPU power identical during your test? At those speeds, the encryption/decryption overhead might not be trivial. You might want to retry the tests without SSH and see what kind of difference it makes.

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