On Sunday November 13, brad@xxxxxxxxxxx wrote: > G'day all, > > Here is an interesting question( well I think so in any case ). I just replaced a failed disk in my > 15 drive Raid-6. > > Simply mdadm --add /dev/md0 /dev/sdl > > Why, when there is no other activity on the array at all, is it writing to every disk during the > recovery? I would have assumed it just read from the others and > write to sdl. The raid6 recovery code always writes out the P and Q blocks for every stripe. This is un-necessary and there is in fact a comment in the code saying: /**** FIX: Should we really do both of these unconditionally? ****/ I recently reviewed and cleaned up this code, though I haven't tested the new version yet. I'll make sure the new code doesn't do un-necessary writes (it may already not). So there is a good chance that 2.6.16 will do a better job here. Thanks for the report, NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
