[Beowulf] Re: Cooling vs HW replacement

Karen Shaeffer shaeffer at neuralscape.com
Fri Jan 21 13:13:52 PST 2005

On Fri, Jan 21, 2005 at 03:10:31PM -0500, Robert G. Brown wrote:
> Has anyone observed that a megahour is 114 years?  Has anyone observed
> that this is so ludicrous a figure as to be totally meaningless?  Show
> me a single disk on the planet that will run, under load, for a mere two
> decades and I'll bow down before it and start sacrificing chickens.
> Humans don't live a megahour MTBF.  Disks damn sure don't.

Yes. Well put.

The only number that has any meaning to a disk drive manufacturer is the
warranty time. The disk drive business is highly competitive and technology
intensive. Profit margins are razor thin. A minimal uptic in warranted
failure rates will have a significant impact on drive manufacturer's bottom
line. They go to great pains to ensure the product works for as long as the
warranty, under the prescribed operating conditions.

Those MTBF numbers are projections based on sophisticated thermal cycling
methods employed witin the set of QA processes used on disk drives. They
run those drives in ovens, cycling them though a wide array of temperature
variances and durations, leading to the projections. Internally, those
disk drive companies only care that the drive lasts until the warranty

 Karen Shaeffer
 Neuralscape, Palo Alto, Ca. 94306
 shaeffer at neuralscape.com  http://www.neuralscape.com

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