"Fast Switching" or NIC-to-NIC communications AND channel bonding discouragement

[Bogdan Costescu]

On Sat, 11 Mar 2000, Brian Dushaw wrote:

> On a similar topic, I have tried channel bonding with the 2.2.x kernels
> (T. Davis' patch) and found that it was only marginally effective (and
> not effective at all for MPI or pghpf parallelizations - things got worse).
> There is some suggestion that this has to do with the "stack [??]"
> inefficiencies of the 2.2.x kernels, that is better in 2.3.x [but what do
> I know of this? nothing...]  Does anyone have any wise words for better
> channel bonding performance?

How have you tested the channel bonding? Did you use netperf, ttcp or a
similar tool?

You only get an improvement for MPI parallelizations if your software
sends a lot of data, but not very often which means that you need more
bandwidth and you don't care about latency. The channel bonding improves
bandwidth allowing you to treat n NICs as one and thus increasing the
bandwidth, but does not modify the TCP stack (which is responsible for the
high latency). For more info about this subject, you should check
www.beowulf.org and its associated mailing lists.

I'm using channel bonding since its announcement on the beowulf list (that
is, the new version 0.2 which is now included in the 2.2 series) without
problems in a file-server.

Best regards,

Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu@IWR.Uni-Heidelberg.De

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