h1. Mdadm add new disk

Remove fail drive

mdadm --manage /dev/md0 --fail /dev/sda1
mdadm --manage /dev/md0 --remove /dev/sda1

Rescan new disks attached for i in {0..3}; do echo “- - -“ > /sys/class/scsi_host/host${i}/scan; done

Add new drive

parted /dev/sdc mklabel msdos
parted /dev/sdc mkpart primary 2048s 100%
parted /dev/sdc set 1 raid on
parted /dev/sdc unit s p
mdadm --manage /dev/md0 --add /dev/sdc1

To avoid this run mkdevicemap “/usr/sbin/grub-probe: warning: Couldn’t find physical volume `(null)’. Some modules may be missing from core image…”

grub-mkdevicemap -n

Install grub

grub-install --recheck /dev/sda

Debug with

mdadm -D /dev/md0
cat /proc/mdstat