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

Diego M. Vadell dvadell at linuxclusters.com.ar
Mon Sep 15 21:42:36 EDT 2008


On Monday 08 September 2008 21:30:03 Rahul Nabar wrote:
> 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.
>

Hi,

   A month ago I spent an awful lot of time trying to debug something like 
that: I was trying to tune two linux boxes to make the perform better with a 
satellite link (700ms delay).

   turned out that ssh is not the right tool to test the network. From 
http://www.psc.edu/networking/projects/hpn-ssh/

"SCP and the underlying SSH2 protocol implementation in OpenSSH is network 
performance limited by statically defined internal flow control buffers. 
These buffers often end up acting as a bottleneck for network throughput of 
SCP, especially on long and high bandwith network links. Modifying the ssh 
code to allow the buffers to be defined at run time eliminates this 
bottleneck. We have created a patch ..."

   I started testing with wget in one side and an apache in the other, and 
everything went back to what I expected.

   so my advice is: test the network with something else, but not ssh nor scp.

HIH,
 -- Diego.

   
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