Vincent, Don't forget that between SDR and QDR, there is DDR. If SDR is too slow, and QDR is too expensive, DDR might be just right.
-- Goldilocks On 11/07/2011 11:58 AM, Vincent Diepeveen wrote: > hi Prentice, > > I had noticed the diff between SDR up to QDR, > the SDR cards are affordable, the QDR isn't. > > The SDR's are all $50-$75 on ebay now. The QDR's i didn't find cheap > prices in that pricerange yet. > > If i would want to build a network that's low latency and had a budget > of $800 or so a node of course i would > build a dolphin SCI network, as that's probably the fastest latency > card sold for a $675 or so a piece. > > I do not really see a rival latency wise to Dolphin there. I bet most > manufacturers selling clusters don't use > it as they can make $100 more profit or so selling other networking > stuff, and universities usually swallow that. > > So price total dominates the network. As it seems now infiniband 4x is > not going to offer enough performance. > The one-way pingpong latencies over a switch that i see of it, are not > very convincing. I see remote writes to RAM > are like nearly 10 microseconds for 4x infiniband and that card is the > only one affordable. > > The old QM400's i have here are one-way pingpong 2.1 us or so, and > QM500-B's are plentyful on the net (of course big disadvantage: needs > pci-x), > which are a 1.3 us or so there and have SHMEM. Not seeing a cheap > switch for the QM500's though nor cables. > > You see price really dominates everything here. Small cheap nodes you > cannot build if the port price, thanks to expensive network card, > more than doubles. > > Power is not the real concern for now - if a factory already burns a > couple of hundreds of megawatts, a small cluster somewhere on the > attick eating > a few kilowatts is not really a problem :) > > > > On Nov 7, 2011, at 5:36 PM, Prentice Bisbal wrote: > >> >> On 11/06/2011 06:01 PM, Vincent Diepeveen wrote: >>> hi, >>> >>> There is a lot of infiniband 4x stuff on ebay now. >> >> Vincent, >> >> Do you mean 4x, or QDR? They refer to different parts of the IB >> architecture. 4x refers to the number of lanes for the data to travel >> down and QDR refers to the data signalling rate. >> >> It's probably irrelevant for this conversation, but if you are just >> learning about IB, It's good to understand that difference. >> >> Prentice >> _______________________________________________ >> 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 > _______________________________________________ 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
