Beowulf - Single Board Computers? (long)

[Greg Lindahl]

> OK, so this is something I know a little about; I've been
> wanting to use SBCs for a Beowulf system for some time now,
> and have been shopping the SBC market for a couple of years.

Well, I'm not sure if your restriction to "S"BC is killing you or
what, but:

1) Alta Technologies does sell a quite compact rackmount system built
out of a conventional motherboard, so it's quite cheap and uses
whatever today's hottest motherboard is. I think that there are other
vendors out there selling systems which have a 90 degree "bus bender"
that allows you to have 3.5 inch thick systems (www.aspsys.com), again
using cheap commodity motherbaords. The 3rd company I know of in the
cluster market, Paralogic (www.xtreme-machines.com), seems to only
sell a relatively compact conventional case with cards at right
angles, which is about as big as a normal pile of PC's. (Hey, Doug,
check out small cases. They're cool, and they are required to be able
to bid on my latest $400,000 RFP.)

2) Many _military_ vendors sell relatively small systems built on
custom boards. They are very pricy but they are modern in their
performance. Two example vendors of these are Alta and Mercury. And
no, they don't have the limitation of "no communications or minimum 6
boards"; they both are compact and still include 100 mbit and Myrinet
options.

Perhaps the "industrial computer" segment is very different from the
military segment. I don't see any of the military vendors in your url
listing.

>    * While all this ad-hoc stuff might work out well,
>    what would be unbelievably cool would be to write
>    a LAN-on-PCI implementation for Linux, that would
>    work with CompactPCI.

Why? I'd much rather have ethernet or Myrinet; switches always kill
busses. For example:

>    Since CompactPCI can
>    handle longer backplanes than card-edge PCI, you
>    could potentially get lots of CPUs in a single
>    rackmount enclosure, with a 133MBps network
>    backplane.

Which isn't that great; switched 100 mbit ethernet can quickly have a
lot more total bandwidth than that. The actual performance of a
lan-on-pci would probably be ~ 25% of peak, but we know we can get near
100% of peak out of switched ethernet. So the cross-over point is
at... 3 cpus. And ethernet is cheap, cheap, cheap.

> Not that any of this, AFAIK, is remotely
>    possible today.

CompactPCI-based systems are exactly what Alta sells into the military
market. They are expensive enough that they have a separate product
they sell to the cluster market. I'd be willing to bet that most of us
are so cost-conscious that we won't want to pay for anything but a
commodity board in a space-saving case, which seems to be pretty cheap
today.

-- g