[Beowulf] Re: Beowulf Digest, Vol 25, Issue 9

[Ed Karns]

On Mar 3, 2006, at 12:53 PM, beowulf-request at beowulf.org wrote:

> O.K. So  Option 3 -- 32 desktops from HP or Dell-- is eliminated  
> because I cannot afford to upgrade the air conditioning unit in the  
> room
> available and I cannot afford an onsite service contract to cover  
> repair costs.

Trade offs: air conditioning or service contract or both? Without a  
good cool air source (colder than ambient temp), the service contract  
becomes almost mandatory. If you can engineer great ventilation with  
lots of cooler air entering the farm, you might be able to skate on  
both air conditioning and service contracts. Change the room air 2 to  
4 times per hour or keep ambient room air from exceeding 90 F. with  
reasonable good circulation around the systems. Sometimes a good,  
easily opened sky light with a good sized exhaust fan will solve a  
world of circulation problems. Paying attention to the original heat  
load generation will save huge amounts of expense.
Often overlooked: extra large CPU power supplies run cooler. If  
standard power supplies run warm to the touch (100 F. +), upgrading  
to 50 % larger will reduce heat loads (300 watt upgraded to 450 watt  
supply). A CPU that only needs 200 watts will only consume that 200  
watts, no matter the size of the supply ... and a 300 watt supply  
"stressed" to 60% of rated load will run warm, but a 450 watt supply  
running at 45% of rated duty will not produce nearly as much heat ...  
and the larger will last longer. (Alternative below)
Sometimes overlooked: larger, older monitors run warmer than small  
ones or cheap flat screen LCD monitors. (Big monitors are needed only  
to sell the next round of grant refinancing. :>)
Not to be ignored: Larger gauge power wires are cooler. This may seem  
like micromanagement, but 32 systems feed by 32 sets of #16 gauge  
plug strips and power lines will also generate some heat. Spending  
10% more for fewer #12 gauge power feeds might save enough to be  
important. Healthier power / surge strips, larger circuit breakers =  
same, same.

> In response to RGB's request for more information: Here are my  
> budgetary constraints and my needs
>
> Budget ~US $25K, with the possibility of $5K ...  My  
> simulations ... require in excess of 512 MB of memory ... ideally  
> twice that amount. ... should go for gigabit ethernet.

Yes ... 32 CPUs w/ 512K RAM plus several flat screen monitors.  
Assuming ISA style "mini tower" boxes, 2 to 3 GigaHertz each, would  
have a total heat load requirement of around 6000 watts (running) ...  
could be offset by two window mounted air conditioners ... US$400 to  
$500 x 32 = US$12K to US$16K+, plus accessories and power lines and  
air conditioning and installation and service, etc., etc. ... quite  
possibly a budget buster.

A possible alternative: Last week Apple announced the newer version  
of the Mac Mini ...  meaning that the previous models could shortly  
be picked up quite reasonably ...  and picking up a number of these  
[1.25 or 1.4 GigaHertz, 512K RAM (upgradable), ethernet and FireWire  
equipped, 50 watt (observed, running)] systems ... is certainly food  
for thought ... as the FireWire ports as fast or faster than  
1000baseT ethernet and work with Apple's own "beowulf  
scenario" (http://www.apple.com/xserve/workgroupcluster/) or if  
preferred a Linux variant ( yellowdoglinux.com /  
terrasoftsolutions.com ).

And the heat load of 32 of these could be resolved with a window fan  
and a maintenance contract could be resolved by getting some  
spares ... :>)

Ed Karns
FireWireStuff.com

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