Re: MTBF interpretations (Re: ZFS performance)
>> > Claimed MTBF: 1 million hours. Believe it or not, this is par
>> > for the course for high-end disks.
>> >
>> > 24 hours a day, 365 days a year: 8760 hours per year.
>> > 1000000/8760 = 114 years.
>> >
>> > So, no: MTBF numbers must be presumed to be malicious lies.
>>
>> With your interpretation every single drive would not be allowed to fail
>> before its MTBF value. That's wrong. MTBF is a mean value for all drives
>> of this type, not a guaranteed minimum value for a single drive.
>
> No, my interpretation is that the average (mean) lifetime
> between failures should be the listed value. At 114 years, half
> of the population of drives should still be working.
Sadly, that's a misinterpretation.
What you describe would be called something like life expectancy.
The main problem with MTBF is that it's very often misunderstood.
The other problem is that life expectancy is almost never provided as
a data point, contrary to MTBF, whereas for the vast majority of buyers
(who only buy a single item) life expectancy would be the more
meaningful measure.
Stefan
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