[Beowulf] Lowered latency with multi-rail IB?

[John Hearns]

>From the blurb on SGI MPT -(their ICE systems have multirail)


http://www.sgi.fr/WP_MPT_SGI.pdf


SGI MPT utilizes multiple InfiniBand rails to perform message
pathway distribution and message striping. Message pathway
distribution is done by strategically mapping individual routes
(source to destination) to the available rails. Since routes are
mapped to different rails, more aggregate bandwidth is available
in situations where many MPI processes are communicating
at the same time. SGI MPT performs message striping
by sending portions of large messages on each rail in parallel
with the effect of nearly doubling the effective MPI point-topoint
bandwidth.