The reasons behind 3456 ports and Jonathans opinion about HPC
I had an email in my inbox from a reader, who asked me for the math behind the 300 switches. So i cite the email of Andreas Bechtolsheim to Jonathan Schwartz (Jonathan published it his blog, you will find more information about our Constellation announcement in his blog)
Begin forwarded message:
From: Andreas Bechtolsheim
Date: June 28, 2007 6:58:59 AM PDT
To: Jonathan Schwartz
Cc: John Fowler
Subject: 3,456 We implement a 5-stage fabric, and with a 24-port switching element
the maximum number of ports is n*n/2*n/2, or 24*12*12 =3456. Other Infiniband switches in the market today are 3-stage fabrics
and they have n*n/2 or 24*12 = 288 ports. Now you can build a 5-stage 3456 port switch with 12 288-port switches
and 288 24-port leaf switches but you end up with 300 boxes occupying
about 456U of rack space or 12 racks, and 6912 cables.
We use one double rack with 1152 cables, so it is 1/6th the space,
1/6th the cables and 1/6th the weight. On Jun 28, 2007, at 6:36 AM, Jonathan Schwartz wrote: so - why 3,456 ports?
But this is not the most interesting point Jonathan makes in his blog. He answers the question, why we do such systems:
The academic supercomputing community (there's that word again) sets the pace for enterprise computing across the world – which has grabbed on to HPC for an array of real world challenges, from virus, disease, and drug discovery, to customer purchase pattern analytics, capital markets trading, energy discovery, dynamic resource management - you name it, it's one of the fastest growing segments in the marketplace. Proving that what starts in academia, ends up on main street. Industry looks to academia and research institutions to understand the innovations that enable breakthrough scale and performance (just ask Linus - who, come to think of it, still hasn't responded to my dinner invite... I hope it's not my cooking.)
It´s not only a simple marketing stunt. The problem of HPC in really large scales ist to an part, that these systems need large amounts of labour to build them. Getting from
transforms HPC from an hand-crafted environment to an more commoditized environment, so new sets of customers and problems gets in a economical reasonable reach for HPC systems, thus opening new markets for such environments, thus moving HPC to a more standard tool in the architectural toolbox.