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Subject: Re: [OMPI users] Role of ethernet interfaces of startup of openmpi job using IB
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-09-27 17:30:03

On Sep 27, 2011, at 5:03 PM, Prentice Bisbal wrote:

> To clarify, is IP/Ethernet required, or will IPoIB be used if it's
> configured on the nodes? Would this make a difference.

IPoIB is fine, although I've heard concerns about its stability at scale.

The difference that it'll make is that it's generally faster than ethernet. It never runs at wire IB speed because of the overheads involved, but it's likely to be much faster than 1GB ethernet, for example.

You can specify which interfaces Open MPI's OOB channel uses with the oob_tcp_if_include MCA parameter. For example:

   mpirun --mca oob_tcp_if_include ib0 ...

Jeff Squyres
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