[Beowulf] Opteron cooling specifications?

[Bill Broadley]

I'm writing a spec for future opteron cluster purchases.  The issue of
airflow came up.

I've seen a surprising variety of configurations, some with a giant rotating
cylinder (think paddle wheel), most with a variety of 40x28 or 40x56mm
fans, or horizontal blowers.

Anyone have a fan vendor they prefer?  Ideally well known for making 
fans that last 3+ years when in use 24/7.

A target node CFM for a dual socket dual core opteron?

A target maximum CPU temp?  I assume it's wise to stay well below the
70C or so thermal max on most of the dual core Opterons.

Seems like there is a huge variation in the number of fans and total CFM
from various chassis/node manufacturers.  A single core single socket
1u opteron I got from sun has two 40mm x 56mm, and 4 * 40mm x 28mm fans.
Not bad for a node starting at $750.

Additionally some chassis designs form a fairly decent wall across the
node for the fans to insure a good front to back airflow.  Others seem
to place fans willy nilly, I've even seen some that suck air sideways
across the rear opteron.

In any case, the nature of the campus purchasing process is that we can
put in any specification, but can't buy from a single vendor, or award
bids for better engineering.  So basically lowest bid wins that meets
the spec.  Thus the need for a better spec. 

Any feedback appreciated.

-- 
Bill Broadley
Computational Science and Engineering
UC Davis