On 04/18/2012 03:42 PM, Mark Hahn wrote: >> Aggregation spine? Can you tell me more about that? Can you give me a >> part/model number? > > spine is just the term for the trunk of a fat tree. usually the > per-rack switches are called leaves since if nothing else, they may > not be at the top of the rack, or there may be more than one per rack...
Ahh... gotcha. In the previous e-mail, it sounded like a special line card or something from the context. Tripped up by terminology. > > the good thing about the leaf/spine approach is that it's modular, > and possibly less vendor-locked-in. (not that IB is really > multi-vendor anyway). > > cable-wise, I'm not sure leaf-spine really wins, since you can think > of a chassis switch as a leaf-spine with FR4 rather than CX4. AFAIKT, > the same radix-36 switch is used in each. > > spine/leave can be distributed so that there's no one place where you > get too many cables. My cluster is only 3 racks, with the head-node and IB switch in the middle rack, so the cable don't have too far to go, so switching to top-of-rack switches isn't that big of a deal for me. Of course, my cluster might expand as part of this upgrade. > > "less than fully fat" fabrics seem to be pretty common when taking the > modular approach. for instance, if a 36x switch is split into 24 down > (node) and 12 up, you can put two back-to-back, or have three going > into a single spine switch, or more going into multiple > spines. you could even have some racks with more spineward links. > and in your case, you could vary the number of links going to your > existing chassis switch (though it probably shouldn't be the spine > since all its links are slower...) > > -mark > _______________________________________________ Beowulf mailing list, [email protected] sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
