On 2026-06-21, Paul Leiber wrote: > I managed to rebuild the md RAID1 using the data on the seemingly failed > device (partition_1). First, I did a dd dump of partition_2 (currently in > usage) in order not to lose data. Then, I recreated the RAID1 using the data > from partition_1: > > mdadm --stop /dev/md0 # This stops the degraded RAID1 > mdadm --assemble --update=uuid /dev/md0 /dev/mapper/partition_1 # This > creates a new RAID1 using the partition_1, a new array UUID is required in > order for --assembly to work > mdadm --manage --add /dev/md0 /dev/mapper/partition_2 # This adds partition_2 > to the RAID1, contents of partition_1 are replicated to partition_2 > automatically
Your commands are strange : the partitions should be the disk partitions from /dev and not mapped ones. Or you have another layer ? From where come /dev/mapper/partition_1 and /dev/mapper/partition_2 ? Beside this it is much quicker and safer to go this way : - do not stop the md array (and thus the assemble is not needed) - remove the failed partition mdadm --manage /dev/md0 --remove "failed partition" - add the new clean partition mdadm --manage /dev/md0 --add "good partition" - and let mdadm sync the array
