Software RAID with mdadm

Cheat sheet

• cat /proc/mdstat status (degraded? rebuilding?)
• sudo mdadm --detail /dev/md0
• sudo mdadm /dev/md0 --fail /dev/sdX --remove /dev/sdX mark and remove the failed one
• sudo mdadm /dev/md0 --add /dev/sdY add a disk in its place
• sudo mdadm --grow /dev/md0 --raid-devices=4 grow the array
• sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf save the config