[Beowulf] Cooling vs HW replacement - fans

Jim Lux james.p.lux at jpl.nasa.gov
Mon Jan 17 10:53:39 EST 2005


----- Original Message -----
From: "Alvin Oga" <alvin at Mail.Linux-Consulting.com>
To: "Jim Lux" <James.P.Lux at jpl.nasa.gov>
Cc: "Ariel Sabiguero" <asabigue at fing.edu.uy>; <beowulf at beowulf.org>
Sent: Sunday, January 16, 2005 10:55 PM
Subject: Re: [Beowulf] Cooling vs HW replacement - fans


>
>
> hi ya
>
> > 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


For instance, Cheetah X15s claim 1.2 million hrs mtbf (based on failure
rates from a raft of drives running together, 250 power on/off cycles/yr, at
some case temp)..
The statistics they give look like about 1.4 failures per thousand drives
per month for 720 power on hrs/mo, 250 power on/off cycles/yr, 20% usage and
case temps of around 50C...(they have a chart showing what part of the drive
can be at what max temperature and where the cooling air should go...)

They give the 1.2 million hour number as using 0.92 m/sec (180 linear
ft/min) inlet air at 25C + 5C rise in the enclosure (drive operating in 30C
air)...  I note that this is fairly cool for most computers in a "desktop"
environment.

I'm actually quite impressed by this kind of reliability...




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