Alexander Schreiber [als at thangorodrim.de] wrote:
Yes, that is precisely how I understand the MTBF - if
2 out
of 4 drives die in the first month, well, too bad, that's why
it is called _mean_ TBF. The fact that the manufacturer is
willing to give said 5 years of warranty implies that only a
small (but definitely non-zero) number of those disks
_should_ die within the first 5 years.
It sounds like you've still missed a bit. The MTBF of 136
years doesn't mean that your drive might last 136 years on
average, nor does it mean that if you buy 136 drives you
should expect one failure per year on average.
It means that if you replace each and every drive every time
they reach the end of their service life (usually five years)
*then* you can expect the above things.
So your drive will probably fail one in 136 years *iff* you
swap it out for a brand new drive 27 times (or so) during
those 136 years.
I'll grant you that it also means that the odds of your original
drive failing in those initial five years must also be fairly
small - just nowhere near as small as you might think.
Antonio