1. Create a new RAID array
Create (mdadm --create) is used to create a new array:
mdadm --create --verbose /dev/md0 --level=1 /dev/sda1 /dev/sdb22. /etc/mdadm.conf
/etc/mdadm.conf or /etc/mdadm/mdadm.conf (on debian) is the main configuration file for mdadm. After we create our RAID arrays we add them to this file using:
mdadm --detail --scan >> /etc/mdadm.conf
or on debian
mdadm --detail --scan >> /etc/mdadm/mdadm.conf
3. Remove a disk from an array
We can’t remove a disk directly from the array, unless it is failed, so we first have to fail it (if the drive it is failed this is normally already in failed state and this step is not needed):
mdadm --fail /dev/md0 /dev/sda1
and now we can remove it:
mdadm --remove /dev/md0 /dev/sda1
This can be done in a single step using:
mdadm /dev/md0 --fail /dev/sda1 --remove /dev/sda1
4. Add a disk to an existing array
We can add a new disk to an array (replacing a failed one probably):
mdadm --add /dev/md0 /dev/sdb1
5. Verifying the status of the RAID arrays
We can check the status of the arrays on the system with:
cat /proc/mdstat6. Stop and delete a RAID array
If we want to completely remove a raid array we have to stop if first and then remove it:
mdadm --stop /dev/md0
mdadm --remove /dev/md0
and finally we can even delete the superblock from the individual drives:
mdadm --zero-superblock /dev/sda
