> Even if the particular part of the device is unreadable, the operating system is supposed to try to write the correct data over the top. According to md(4) m

> Even if the particular part of the device is unreadable, the operating system is supposed to try to write the correct data over the top. According to md(4) man page, that's what it does. Only if the write fails, it is added to the bad block list. FWIW, I've also encountered an issue related to BBL - in my case multiple RAID6 components got bogus bad blocks (no idea from where, maybe a lower-level controller issue or driver bug?) so there were logical sectors that had insufficient non-"bad" backing sectors and the RAID array reshape process code was seemingly not prepared for that, entering an infinite loop with 100% CPU use and locking all use of the array.