[RndTbl] hard drive failure curve

Adam Thompson athompso at athompso.net
Wed Sep 3 14:53:21 CDT 2014


The obvious analogy that for obvious reasons* won't have occurred to you: cars.  If you don't get a lemon, it's probably good for a while, but eventually starts to break down.
Also, historically, humans - at least in ages and places where infant mortality is/was a significant drag on population growth.

-Adam

*for those of you who don't know Trevor well, his 25(?)-year-old car is lovingly & painstakingly maintained in near-new condition.

On September 3, 2014 2:10:53 PM CDT, Trevor Cordes <trevor at tecnopolis.ca> wrote:
>OK, so you know how many (most?) computer components' failure rates
>follow the "bathtub curve":
>
>http://users.ece.cmu.edu/~koopman/des_s99/sw_reliability/Image1.gif
>
>They either die quickly due to egregious manufacturing faults, or live
>a long time (near 0% failure rate), and then all start dying as they
>get
>really old.
>
>The bathtub curve occurs in tons of places, like with a simple light
>bulb.
>
>As per my experience (probably dealing with over 1000 drives
>personally), and google's studies, as well as anecdotal information,
>hard drives are different.  The failure rate seems to be bathtub-ish.
>The initial failure rate is fairly bathtub.  But the useful-life period
>is at a much higher level and seems to grow slightly, meaning instead
>of dropping to near-zero failures during useful life, they drop to
>around 15% failure rate each year, mostly independent of age.  Then,
>in the old-age phase they seem to ramp up much slower towards death.
>It's not a hockey-stick right edge, it's more a constant gentle hill
>slope.  We all have seen many drives that are still running after 8,
>10, 20 years.  In fact, it seems more of a survival of the fittest
>system (maybe like turtles?), where once they live to a certain age,
>many go on to live far beyond the average.
>
>Anyhow, my question is, what else in the non-computer world has a
>failure graph like hard drives?  Something easy for a neophyte to
>grasp.
>Normal bathtubs have lightbulbs.  What analogy can be used for hard
>drives?  I haven't been able to think of any!
>
>Surely there must be one??
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-- 
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