[hiatus]

Surprised by the number of drives with 0 failures, though it seems not all of the drives were run for the required time to qualify for the rating.

> In Q3, six different drive models managed to have zero drive failures during the quarter. But only the 6TB Seagate, noted above, had over 50,000 drive days, our minimum standard for ensuring we have enough data to make the AFR plausible.

[kqr]

I have always wondered why they don't use techniques from survival analysis to be able to draw conclusions even from sets with lower failure rates. Or for that matter to avoid slight bias even for drives they do report.

[andy4blaze]

Andy Klein from Backblaze here. We have done some survival analysis (kaplan-meier curves). In our case, we need to have a reasonable number of failures over the observation period to get decent results. You can take a look at some of our work here: https://www.backblaze.com/blog/hard-drive-life-expectancy/ and see if that is what you were expecting.

[kqr]

Yes! Thank you. I've been thinking about scratching this itch myself but it turns out you did already.

In particular the shape of the survival curve interests me -- you hear so many things about exponential here, bathtub there, but ver little data. I will read once I have a spare moment.