Find the active arrays in the /proc/mdstat:
cat /proc/mdstat
Personalities : [raid0] [linear] [multipath] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid0 sdc[1] sdd[0]
209584128 blocks super 1.2 512k chunks
unused devices: <none>
Unmount the array, stop it and remove it
sudo umount /dev/md0 sudo mdadm --stop /dev/md0 sudo mdadm --remove /dev/md0
Find the devices that were used to build the array with the following command:
lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT NAME SIZE FSTYPE TYPE MOUNTPOINT sda 100G disk sdb 100G disk sdc 100G linux_raid_member disk sdd 100G linux_raid_member disk vda 20G disk ├─vda1 20G ext4 part / └─vda15 1M part
Reset the disks back to normal
sudo mdadm --zero-superblock /dev/sdc sudo mdadm --zero-superblock /dev/sdd
or
sudo wipefs -a -f /dev/sdc sudo wipefs -a -f /dev/sdd
Remove any of the persistent references to the array. Edit the /etc/fstab file and comment out or remove the reference to your array. Also, comment out or remove the array definition from the /etc/mdadm/mdadm.conf file.
. . . # ARRAY /dev/md0 metadata=1.2 name=mdadmwrite:0 UUID=7261fb9c:976d0d97:30bc63ce:85e76e91 . . .
Finally, update the initramfs again
sudo update-initramfs -u
To get started, find the identifiers for the raw disks that you will be using
lsblk -o NAME,SIZE,FSTYPE,TYPE,MOUNTPOINT NAME SIZE FSTYPE TYPE MOUNTPOINT sda 100G disk sdb 100G disk sdc 100G disk sdd 100G disk vda 20G disk ├─vda1 20G ext4 part / └─vda15 1M part
Create RAID1 and create the filesystem
sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdc /dev/sdd mkfs.ext4 -F /dev/md0
You can ensure that the RAID was successfully created by checking the /proc/mdstat file:
cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid0 sdd[1] sdc[0]
209584128 blocks super 1.2 512k chunks
unused devices: <none>
Add the reference to fstab (/data is the existing mount point on my system)
echo '/dev/md0 /data ext4 defaults,nofail,discard 0 0'>>/etc/fstab
To make sure that the array is reassembled automatically at boot, we will have to adjust the /etc/mdadm/mdadm.conf file. You can automatically scan the active array and append the file
sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf #sudo mdadm --examine --scan --config=mdadm.conf >> /etc/mdadm/mdadm.conf
Afterwards, you can update the initramfs, or initial RAM file system, so that the array will be available during the early boot process:
sudo update-initramfs -u
Check if new space is avaliable
df -h
Note For some reason, ubuntu ignores the name md0 on the next boot, and renames the array to md127. You can check with mdadm –query –detail /dev/md*