[Beowulf] using two separate networks for different data streams

[Mark Hahn]

> > I tend to think of IB as mainly for high-bandwidth, since afaikt its 
> > latency isn't even as good as myri 2g (mx, 3 us).  to say nothing of 
> > myri 10g, quadrics, numalink, sci.
> 
> I know some people don't think of InfiniPath as being InfiniBand, but
> really, Mark, I didn't think you were one of them! ;-)

hmm, I had the impression that InfiniPath operated in either fast
InfiniPath-to-InfiniPath mode, or in slow generic IB mode.  that is,
that in "fast" mode, it was mostly just recycling IB phy layers.

> In any case, yes, you are correct for Mellanox InfiniBand HCAs, but
> not for InfiniPath.

so if Mellanox IB has latency X, and InfiniPath has Y,
the expected latency between the two is around (X+Y)/2?