Does anyone remember what is their definition of "drive failure"? Is it SMART "failure imminent" report, single uncorrectable read error or complete data loss for a whole disk? I recall reading about it in one of their previous report, but can't find it again.
EDIT: nevermind, found it.
"Backblaze counts a drive as failed when it is removed from a Storage Pod and replaced because it has 1) totally stopped working, or 2) because it has shown evidence of failing soon.
A drive is considered to have stopped working when the drive appears physically dead (e.g. won’t power up), doesn’t respond to console commands or the RAID system tells us that the drive can’t be read or written."