[Beowulf] Cooling vs HW replacement - fans

[Alvin Oga]

hi ya

On Sun, 16 Jan 2005, Jim Lux wrote:

> > Is it worth cooling down the room to a Class A Computer room standard or
> > save the money for hardware upgrade after three years? In warm countries
> > keeping 18ºC the air inside a room (PC-heated) when outside temperature
> > is 30ºC average it becomes pretty expensive to pay electricity bills. It
> > is cheaper to "circulate" 30ºC air and have from 40-50ºC inside the
> chassis.
> 
> Fascinating system design question....

we had some 1Us where the clients put it in a harsh 99%
enclosed environment
	- 150F is the ambient operating ( normal ) temp and running 24x7
 	- the ide disks ( basically all ) died within 1yr
	( cpu/mem/ps all seems fine )

	=
	= circulating hot air will not help
	=	- cooler air needs to come in and hot air must go out
	=

> Such data is very hard to come by, however, a good rule of thumb is that
> life (MTBF) is halved for every 10 degree (C) temperature rise (Arrhenius
> equation).

where the degradation starts from say 25C or 20C .. wherever they spec'd
the mtbf starting point

> I have seen temperature vs MTBF data for disk drives, a google
> or search of a site such as Seagates should find it.

those mtbf, some disks are spec'd at a ridulous 1,000,000 mtbf hrs

>  Of course, they do
> accelerated life testing at elevated temperatures, so there must be some
> analysis that equates X hours of operation at temperature Y to Z house of
> operation at temperature Y-30.  The real question would be what's the life
> limiting component... I'd be willing to gamble (based on personal experience
> with PC failures over the last 20 years) that it's some component in the
> power supply.

i'd put my $$ on the "cheap" fans dying first
	- adding better quality and redundant fans seems to work for 1Us
	in regular operating environment
 
> > Links to this information are highly appreciated!
> > I remember old (40MB RLL disks shipping this information with the
> > device, several pages of  printed manual) hardware showing the
> > difference in MTBF vs environment conditions, but nowadays commodity
> > harware does not consider this on the sticker on the top of the device...
> 
> But it is available at mfr's websites, at least for some components.

yupp

c ya
alvin