[Beowulf] building Infiniband 4x cluster questions - using 1 port out of 2

[Robert Horton]

On Mon, 2011-11-07 at 15:45 +0100, Vincent Diepeveen wrote:
> What's the second one doing, is this just in case the switch fails,
> a  
> kind of 'backup'  port?
> 
> In my naivity i had thought that both ports together formed the  
> bidirectional link to the switch.
> So i thought that 1 port was for 10 gigabit upstream and the other  
> port was for 10 gigabit downstream,
> did i misunderstood that?

It's "normal" to just use single port cards in a compute server. You
might want to use 2 (or more) to increase the bandwidth to a particular
machine (might be useful for a fileserver, for instance) or if you are
linking nodes to each other (rather than via a switch) in a taurus-type
topology.

Rob