[Beowulf] newbie's dilemma

[Mark Hahn]

> Note also that I'm guessing that these boxes draw somewhere between 200
> and 300 watts fully loaded with tasks (anybody out there measure?

I recently did some measurements on new nodes: HP DL145G2's with 8GB ram,
2x80G disks, quadrics elan4 cards:

		2x DC opt/2.2	2x SC opt/2.6
booting         259-317		244-313
idle            265		255
1p thrash -g6	286		275
1p stream	291		284
2p		290-301		310
4p		290-338

"idle" means nothing explicitly running (though the distro includes a 
surprising number of irrelevant daemons.)  "thrash -g 6" is a program that
allocates 6GB and just repeatedly memset's it.  it's single-threaded,
but since 6GB is large enough to require both CPU's banks of memory, the
other cpu is not inactive.  1/2/3 are an openmp version of stream, run 
with "numactl -l".

firing up streaming IO during one of these runs didn't really change 
the power picture at all.  then again, disks are not more than ~15W
when spun up, so this is not a big surprise.