[Beowulf] bring back 2012?

Mark Hahn hahn at mcmaster.ca
Mon Aug 22 14:30:08 PDT 2016

> FWIW the direct contact solutions (wether they use water or some other
> dielectric fluid) as far as I can see have several main problems
> * complexity (all that plumbing and getting it to 8 phi's + 2 cpu's all
> crammed in 2RU)
> * nodes have to be modified after the come out of the factory

for boutique stuff like you describe, direct-contact would seem
problematic if also assuming low volume.  if G wanted to build 
100k identical boxes, even fancy ones, different story.

> * not all the components are cooled (ie. ram, disks etc)  You still have
> to run some form of air cooling.

lots of systems have no disks, and I'm expecting at least a few large
systems in upcoming generations to have no dimms (ie, just HBM).
of course, these properties make the system increasingly specialized,
therefore of less general interest.

it's also true that disks/ram/nic are quite low-power compared to cpus.
something like 1-3W/dimm, 5-10W/disk - versus 130W/cpu.

> see how they will be price competitive, given all the modifications that
> are needed to the systems (I've had pricing for a single rack system but

what's surprising to me is that vendors haven't self-organized to promote
a direct-contact standard.  for instance, suppose each vendor just did 
an version that mated heat pipes to a plate on the side of the chassis.
(water or fluid of your choice would flow through the rack.)

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