On Thu, May 25 2017, Andreas Klauer wrote: > On Wed, May 24, 2017 at 12:12:32PM +1000, NeilBrown wrote: >> What does work is: >> # start with a degraded array, device 0 missing >> mdadm --grow /dev/md42 --array-size=..... >> echo frozen > /sys/block/md42/md/sync_action >> mdadm /dev/md42 --add /dev/loop0 >> echo 0 > /sys/block/md42/md/dev-loop0/slot >> mdadm --grow /dev/md42 --backup-file=... --raid-devices=4 > > Wow. Thanks. > > This should merge Step 1+2, but not Step 3, right? Right. Doing step 3 at the same time is not possible. NeilBrown > > I really need to take a closer look at the things in /sys/.../md/... > > Seems like you can do great things with it... terrible, yes, but great. > > ( > Step 3 would be turning slot 4 to-be-spare into slot 0, > without --add ing another device at all. > > That's what would happen if /dev/loop0 was actually backed > by and thus identical with the slot4 device. > > But that's playing dirty. > ) > > Regards > Andreas Klauer
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