[Beowulf] let's standardize liquid cooling

[Mark Hahn]

> the extra cost to buy 1U nodes and racks.  It is my impression that the
> ratio of costs of 1U nodes versus tower cases has changed.  Is my
> impression correct?  Or perhaps it is just that clusters are getting
> bigger so that tower computer cases on bookcases would require the area

for me, it's largely a question of front surface area.  a small
shoe-box-like chassis would have about the same front size as a 1U.
I think most current DC designs require 1 nodes in 1U.  but yeah,
square nodes would be fan-friendlier - a fact not lost everywhere:
http://www.zdnet.com/inside-facebooks-lab-a-mission-to-make-hardware-open-source-7000004557/
(the "sled server")