Ok, i think i did a mess. I have a 3 way mirror with 3 drives on it All drives are working, not failed. I would like to replace one of these drive (because it's very old) with a new drive. I would like to to the add and replace in the same phase, without reducing the redundancy level I did this multiple times before, during the sync, the array is a 4 way mirror BUT this time i think i did an issue, i've just run this: $ mdadm /dev/md0 --add /dev/sdd1 --replace /dev/sda1 --with /dev/sdd1 sda was marked failed immediately, and sdd1 is marked as active sync. Less than 1 second. Is this ok or i've just added a blank drive and forced the removal of a working one ? Honestly, and this is something that comes to mind right now, the partition is very very small, like 64MB so 1 second sync (on a SSD) could be ok. but: 1. which is the right command to run to add-sync-remove a not-failed disk ? 2. how can I ensure that sdd is working as expected and data were synced properly?
