mdadm cheatsheet

1. Check raid status
   cat /proc/mdstat
   or
   watch cat /proc/mdstat
2. Scan configuration
   mdadm --detail --scan

3. To Remove a disk from the Array, you’ll have to fail then remove the drive.
   mdadm --fail /dev/mdX /dev/sdX
mdadm --remove /dev/mdX /dev/sdX
4. To add a disk to the array:
   mdadm --add /dev/mdX /dev/sdX
5. • Turn bitmap on
     mdadm --grow --bitmap=internal /dev/mdX
   • Turn off bitmap
     mdadm --grow --bitmap=none /dev/mdX
6. Speed up recovery
   echo 50000 > /proc/sys/dev/raid/speed_limit_min

Resources

• http://www.ducea.com/2009/03/08/mdadm-cheat-sheet/
• mdadm man pages