mdadmin

Rescan md-device

mdadm --assemble --scan

Stop md-device
Stop all service using device, samba, nfs

mdadm --manage --stop /dev/md0

Readd md-device

mdadm --manage --add /dev/md0 /dev/sdc2

Force Assemble

sudo mdadm –assemble –run –force /dev/md127 /dev/sd[abdc]3