Subject: /. The Space Simulator Cluster

[Mark Hahn]

> lanl's web page says the per node price was under $1k.  So with 294 nodes and
> a $500k total price, they've still got over $100k to spend on switches and
> wire racks.

the racks, of course, are dead cheap (costco, $100 or so).

> effective to me.  A 1U or 2U rack case is just as dense as those shuttle
> boxes.

hmm, 1U is 19" x 1.75 = 214.5 sq cm of "rack surface area".
xpc is 20x28.5cm=370 sq cm
an "ultraslim" desktop from HP (eg) is 218 sq cm.

so yes, xpc's use somewhat larger space.  that's hardly a bad thing, since 
if you were really interested in density, you'd be using blades.  airflow
might well be easier to manage with these.

the real question is: how reliable are they?  if you figure that they have
two 50Khour fans in each unit (PS and CPU/heatpipe), they'll be replacing 
a unit every 3.5 days.  no doubt they'll have a pile of spares, but it's 
still something of a pain.

> With a dual CPU board you could get by with half the number of Gb
> switch ports, which aren't cheap for >24 port switches.

true, but your linpack score would probably also go down...