Top node hotter than others?

David Mathog mathog at
Fri Jul 25 14:45:21 EDT 2003

> Do the systems have anything similar to Insight Manager
> to indicate the rate of your fans? 

"sensors" shows that. The CPU and two chassis fans
in the various systems are within a few percent of each other.
I can't read the power supply fans though.


node   cpu  Fan1 Fan2
19     4720 4425 4474
20     4720 4377 4377

> Do the cabinets have fans overhead to draw the warm air out? 

Not installed but there's a panel that comes off
where one could be put in.  When that panel is removed 
there's not much metal holding heat on the top of the system,
but the top node only cooled off about 1 degree and no
effect at all on the other nodes.  There's a hole in the bottom
of the case where cool air can go in.  The front is
currently completely open, and the back is open but it's about
8" from a wall.  It's about 4 feet from the top of the top node
to the acoustical tile, and there's a return vent
only 4 feet away, off to one side.  (Yes, I've thought
about moving that return vent directly over the rack.)

I think the hot air is rising, but not very fast, so that it
lingers around the top of the rack no matter what.  You
are probably correct that a fan to pull it off faster
would help.  I'm beginning to think of the rack as a sort
of poorly designed chimney - the kind that doesn't "pull"
well and results in a smokey fireplace.

> Are all 20 nodes purely compute

yes, the master node is across the room.

> As clusters become larger and more dense there is a great deal of
> research going on in various labs, to ensure stability of
> temperatures not just within cabinets, but across entire
> computer rooms. 

Racks should probably plug into chimneys - take all that
heat and vent it straight out of the building. Heck of
a lot cheaper than running A/C to cool it in place. We've got
old fume hood ducts somewhere up above the acoustic ceiling
that go straight to the roof, but the A/C guys didn't
like my chimney idea much because apparently it would
screw up airflow in the building.  Plus a bit
of negative pressure could suck the output from another
lab's fume hood back into my area, which isn't
an attractive prospect.

> growing issue. Have you dealt with any of the majo
> manufactures specific
> to this or any other concerns as your research clusters grow?

The cluster is big enough for now.  Growth is pretty
limited in any case by available power, A/C capacity,
my tolerance for noise since I have to work in the
same room, and of course, $$$.


David Mathog
mathog at
Manager, Sequence Analysis Facility, Biology Division, Caltech
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