An md/raid6 data corruption bug

Posted Aug 25, 2014 20:39 UTC (Mon) by mathstuf (subscriber, #69389)
In reply to: An md/raid6 data corruption bug by dlang
Parent article: An md/raid6 data corruption bug

> If drives have a 12% chance of dieing each year (rough figure from the big studies several years back), that's 1% a month, or ~.2% per week per drive

Is that 12% for each drive or 12% of drives are expected to die (on second thought…is there a difference?)? If the latter, did you get 1% per month from 12% / 12 or (1 - (1 - .12) ^ (1 / 12)) == 1.06%? The latter seems more accurate, but that's mainly my gut feeling here. As an example, with a 50% failure rate becomes 5.6% per month instead of 4.17% because you expect ~94.4% to survive each month until you're left with 50% still around. Then again, drives are independent (…ish), so maybe just straight division is better there. Anyways, leaving it here for a second thought on it.