>> I've seen architectures with two network switchs, one is used for I/O >> (writing, reading, so on) and another for message passing (MPI). how is >> this achieved? I get the idea, from one place, where the applications >> running must be aware of this but I was thinking that for this to work >> it >> must be transparent to the application. How can this be achieved? > > in short: you assign a different IP to each interface (as normal). > it's convenient to use one non-low-order in the IP to distinguish, > and also nice to have separate hostnames like node1 and node1-mpi. > > 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.
Indeed, an excellent question. It seems logical, does it really help though (or do I just feel clever about using the extra Ethernet Port) I can see that if you have a lot of monitoring traffic that might cause an issue, but I have never tested that notion as well. Of course it all depends... I wonder if a dual Ethernet node would be better served by something like a FNN (http://aggregate.org/FNN/) Tim Mattox can probably weigh in on this. -- Doug > hahn> regards, mark hahn. > > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org unsubscribe> To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > -- Doug _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
