[Beowulf] using two separate networks for different data streams

[Daniel Pfenniger]

Ricardo Reis wrote:
> 
> First, Hi all and thanks for your answers. Were truly useful. Which
> brings me to...
> 
> On Fri, 27 Jan 2006, Mark Hahn wrote:
> 
>> I wonder whether anyone has critically evaluated whether this is
>> important.
>> cluster people I talk to like to say fuzzy things like "separate networks
>> make the cluster breathe better".
>>
>> as much as I admire car analogies, I observe that when apps are doing IO,
>> they tend not to be doing MPI.  if your workload is like that, bonding
>> rather than partitioning would actually improve performance.  I wonder
>> whether the partitioning approach might actual reflect other constraints,
>> such as using half-duplex hubs, or low-bisection networks.

The network for MPI should in many cases have low latency, so is expensive
(Myrinet, InfiniBand, etc.) in regards of Ethernet.  The I/O, NFS and
system network does not need low latency, and so for bargain cost can be
added, with the additional ground that it provides a control network to
tweak the nodes remotely when the expensive low latency network is down.

	Dan