[Beowulf] ethernet bonding performance comparison "802.3ad" vs Adaptive Load Balancing

Rahul Nabar rpnabar at gmail.com
Mon Sep 8 20:30:03 EDT 2008


I was experimenting with using channel bonding my twin eth ports to
get a combined bandwidth of (close to) 2 Gbps. The two relevant modes
were 4 (802.3ad) and 6 (alb=Adaptive Load Balancing). I was trying to
compare performance for both.

Before running any sophisticated tests by netperf etc. I just tried to
copy a large file via scp and timed the two file-copies.

Option1:
from node1 to node2. Both nodes have their twin ports bonded together
as bond0 with mode=4 (802.3ad).

They are connected via a Dell PowerConnect 6248 switch. Configured the
switch so that I have two LAG groups combining the two ports coming
from the same node. LACP was turned on.

Option2:
from node3 to node4. Use mode=6 (alb=Adaptive Load Balancing) No
special switch config. No LAG. No LACP.

Result: For a 4GB file-transfer. Both modes took the same time; approx
1min26 sec.

These results are very mystifying to me. I was expecting mode4
(802.3ad ) to be almost twice as fast since it is the only mode which
truly aggregates the twin channels. It ought to be the only one
effective for a peer-to-peer communication (mode 6 would only help
while talking with more than one peer)

Any comments? Also the net file transfer speed seems way lower than
what I'd expect from a close to 2 Gbps connect; even accounting for
the protocol overheads. Do other people have some numbers for me from
their systems?

--
Rahul
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