Creating RAIDs

Jurjen Bokma

September 2010

All copy-pasted from the RAID Wiki: In /etc/mdadm/mdadm.conf:

DEVICE partitions

# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes

# automatically tag new arrays as belonging to the local system
HOMEHOST <system>

# instruct the monitoring daemon where to send mail alerts

ARRAY /dev/md0 level=raid1 num-devices=2 devices=/dev/sdb1,/dev/sdc1 spares=/dev/sdd1 UUID=6b0638f4:5e0d924c:84cc9bd1:d1563c47

Then to create the raid:

user@host:~$ sudo mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=2 /dev/sdb1 /dev/sdc1 --spare-devices=1 /dev/sdd1

... and to put it together (I needed to script /etc/init.d/raid that does this at every boot):

user@host:~$ sudo mdadm --assemble /dev/md0

... to test the raid:

user@host:~$ sudo mdadm --manage --set-faulty /dev/md0 /dev/sdc1

(That should get you some mail!) Then to see what the daemon is doing:

user@host:~$ sudo mdadm --detail /dev/md0
user@host:~$ /proc/mdstat

... and to put the RAID back together the way it is supposed to be configured:

user@host:~$ sudo mdadm /dev/md0 -r /dev/sdc1
user@host:~$ sudo mdadm /dev/md0 -a /dev/sdc1