21.05.2026 12:15, Dmitry Smirnov wrote:
Consider configuration where `/home` partition is on 3 HDDs, arranged into mdRAID-1, with a hot spare. Once HDD dies/disappears, a (hot) spare is immediately used to replace bad/missing disk and restore 200% data redundancy. That is what's expected from such array and it is how things used to work on Debian few releases ago.
I wont comment on the bug report as a whole, but want to comment about this particular scenario. If you have 3 HDDs for RAD1, it's much better and reliable to use 3-way raid1 from the beginning, instead of 2-way raid1 + hot spare. This way you eliminate the thin ice in here: if one drive dies and you'll have just one copy left, the probability to encounter second failure (which is now fatal!) increases significantly, since during recovery, *whole* remaining drive has to be read, including areas which hasn't been touched for long, and where you might face some bad sectors. And recovering from *that* situation is significantly more difficult. When you've 3-way raid1, symmetrical, instead, everything works as it should be. And as a bonus, you have better read performance (but at a price of very slightly worse write performance). Also, none of the disasterous scenarious you outlined, wont occur. FWIW, /mjt
