Franc Zabkar wrote in news:gt9b045tqpk3gbj6i28lrqprncec62bge5@4ax.com
> I've been reading this document which is an analysis of Google's hard
> disc failure rates:
>
> Failure Trends in a Large Disk Drive Population:
> http://research.google.com/archive/disk_failures.pdf
>
> It states that "contrary to previously reported results, we found very
> little correlation between failure rates and either elevated
> temperature or activity levels."
>
> Figure 4 "shows that failures do not increase when the average
> temperature increases. In fact, there is a clear trend showing that
> lower temperatures are associated with higher failure rates. Only at
> very high temperatures is there a slight reversal of this trend."
>
> "Figure 5 looks at the average temperatures for different age groups.
> The distributions are in sync with Figure 4 showing a mostly flat
> failure rate at mid-range temperatures and a modest increase at the
> low end of the temperature distribution.

> What stands out are the 3 and 4-year old drives, where the trend for
> higher failures with higher temperature is

> much more constant

Presumably they mean the bathtub figures look like copies of each other.

> and also more pronounced."

What I find much more interesting is the trend reversal from 3rd to 4th
year, while maintaining equal relation between AFR and temperature ranges.
Presumably the weaker brothers fall out of the mix and the rest just lives on
happily.

>
> "Overall our experiments can confirm previously reported temperature
> effects only for the high end of our temperature range and especially
> for older drives. In the lower and middle temperature ranges, higher
> temperatures are not associated with higher failure rates."
>
> Figure 5 suggests that Google's optimum temperature for hard drives is
> between 35C and 40C.
>
> Elsewhere I found this old IBM article:
> http://web.archive.org/web/200005192.../drivetemp.htm
>
> It states that "figure 2 shows the dramatic effect that temperature
> has on the overall

> *reliability*

> of a hard disk drive. Derivations [sic] from a nominal operating
> temperature (assumed to be maintained over the life of a drive)
> can result in a derivation [sic] from the nominal

> failure *rate*.

Hey, there is that favourite word of yours again.

> As the temperature exceeds the recommended level, the
> failure rate increases two to three percent for every one degree rise
> above it. For example, a hard disk drive running for an extended
> period of time at five degrees above the recommended temperature can
> experience an increase in

> failure *rate*

And again.

> of 10 to 15 percent.

> Likewise, operating a drive below the recommended temperature can extend
> drive life."
>
> This last statement is a bit ambiguous. If a hard drive is more reliable
> at a temperature below that which is recommended, then why not
> recommend a lower temperature in the first place? Then again, maybe
> the author's intended meaning was "recommended maximum temperature".
>
> - Franc Zabkar