[Beowulf] Airflow

Andrew Piskorski atp at piskorski.com
Wed Jun 28 11:51:04 PDT 2006

On Sun, Jun 25, 2006 at 03:52:27PM -0700, Robert Fogt wrote:
> Hello beowulf mailing list,
> How much harm does removing the computer case do?  I know computer cases are 
> designed for the air flow, and without them I was wondering if there will be 

In theory, computer cases are designed for good air flow.  How many of
them actually are, well, I don't know.  I've certainly never seen an
airflow specification for a consumer tower case.

> heating problems. My air conditioner will be enough for the amount of heat 
> generated, but will I need circulation fans in the room also?

The short answer is, I don't know.  But, why NOT use some fans?
Installing a 20 inch box fan to blow directly across each mounted
group of N motherboards seems like cheap insurance.

According to my Kill-A-Watt, my dirt-cheap 20 inch, 120 V AC box fan
uses from 79 to 136 Watts depending on its speed.  I assume a better
quality fan would be more efficient for the amount of air it moves.

> I created a test cluster of 8 nodes, removing all the cases and mounting 
> everything onto a wire rack. It works fine with no heat problems. But I am 
> concerned that once I build the entire 100 node cluster there will be 
> problems. The book I am reading on HPC does not go into that detail.
> I was thinking an air purifier that is always on will slowly circulate the 
> air when the air conditioner is off.

I would not place any bets on "slowly" being good enough.  Why would
you want to risk it?  I'd at LEAST walk around with a temperature
probe looking for hot spots.

Your current 8 node cluster sounds interesting, particularly for a
low-cost do it yourself cluster.  Please do find the time to document
it on a web page, with some pictures, etc.

I wonder about electromagnetic interference.  I've heard of genuinely
bare-board (nothing at all between the motherboards) clusters that had
unstable nodes because of it.

If you're serious about mounting 100 bare-board nodes, well, that's an
interesting project.  Others on the list have lectured about the risks
involved in large self-built, self-insured clusters, please do be sure
you've read those and understand what you're getting into.  And then
go for it, and be sure to report back!  :)

Andrew Piskorski <atp at piskorski.com>

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