On 22/05/17 16:30, Nix wrote: > I'll give it a try -- I hit it twice in succession, once with a > --backup-file, once without. Since mdadm does not warn about the lack of > a --backup-file, I guess the statement in the manual that it is > essential to provide one when changing RAID levels is untrue: I suspect > that it's necessary *if* you're not increasing the number of disks at > the same time, but since I'm growing into a spare, adding a > --backup-file only slows it down? I did discuss this with Neil while I wrote it, so I hope I got it right :-) https://raid.wiki.kernel.org/index.php/A_guide_to_mdadm#Array_internals_and_how_it_affects_mdadm aiui, provided you're using a v1 superblock, the data offset means there is spare space on the drives precisely for the purpose (one of then at least) of keeping a backup. So the reshape will start reshaping into the spare space and eliminate the need for the backup - the new version of the stripe will be safely written before the space occupied by the old stripe is required. Cheers, Wol -- 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
