duncan.garland at ntlworld.com
Mon Jun 8 10:40:45 BST 2009
Calculated MTBF figures are not meaningless because they show what the manufacturer expected. The manufacturers base their warranty programmes and even whether or nor to go into production on them, Do you know where I can get some?
---- Raphael Mankin <raph at mankin.org.uk> wrote:
> On Sun, 2009-06-07 at 12:13 +0100, Duncan Garland wrote:
> > I wonder if the problem can be approached from the other end. I wonder if
> > there is a design standard (ISO or such like) which states that a
> > manufacturer should aim for an MTBF of whatever.
> > I'll let you know if I find anything.
> MTBF, when quoted, is largely meaningless. The figures are computed,
> purely theoretical. No-one actually runs a sufficiently large number of
> items for long enough to get meaningful statistics. If they did, they
> would miss the market.
> Imagine having to run, say, 10000 disk drives for five years in order to
> get meaningful MTBFs before you could put them on sale.
> Only people like Google, Microsoft or Yahoo actually have sufficient
> data, and all they can tell you that is *useful* is that some
> manufacturers are, in the long term, better than others. Nothing about
> models that are not obsolete.
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