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Configure RAID 12023/07/17

 
Configure RAID 1 to add 2 new Disks on a computer.
[1] This example is based on the environment like follows.
It shows to install new Disks [sdb] and [sdc] on this computer and configure RAID 1.
root@dlp:~#
df -h

Filesystem                   Size  Used Avail Use% Mounted on
udev                         3.9G     0  3.9G   0% /dev
tmpfs                        794M  580K  794M   1% /run
/dev/mapper/debian--vg-root   77G  1.2G   72G   2% /
tmpfs                        3.9G     0  3.9G   0% /dev/shm
tmpfs                        5.0M     0  5.0M   0% /run/lock
/dev/vda1                    455M   58M  373M  14% /boot
tmpfs                        794M     0  794M   0% /run/user/0
[2] Create a partition on new Disks and set RAID flag.
root@dlp:~#
apt -y install parted
root@dlp:~#
parted --script /dev/sdb "mklabel gpt"

root@dlp:~#
parted --script /dev/sdc "mklabel gpt"

root@dlp:~#
parted --script /dev/sdb "mkpart primary 0% 100%"

root@dlp:~#
parted --script /dev/sdc "mkpart primary 0% 100%"

root@dlp:~#
parted --script /dev/sdb "set 1 raid on"

root@dlp:~#
parted --script /dev/sdc "set 1 raid on"
[3] Configure RAID 1.
# install required tools

root@dlp:~#
apt -y install mdadm
root@dlp:~#
mdadm --create /dev/md0 --level=raid1 --raid-devices=2 /dev/sdb1 /dev/sdc1

mdadm: Note: this array has metadata at the start and
    may not be suitable as a boot device.  If you plan to
    store '/boot' on this device please ensure that
    your boot-loader understands md/v1.x metadata, or use
    --metadata=0.90
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.

# show status

root@dlp:~#
cat /proc/mdstat

Personalities : [raid1]
md0 : active raid1 sdc1[1] sdb1[0]
      83817472 blocks super 1.2 [2/2] [UU]
      [=>...................]  resync =  6.6% (5601664/83817472) finish=6.2min speed=207469K/sec

unused devices: <none>

# status turns like follows if syncing finished
# that's OK to configure RAID 1

root@dlp:~#
cat /proc/mdstat

Personalities : [raid1]
md0 : active raid1 sdc1[1] sdb1[0]
      83817472 blocks super 1.2 [2/2] [UU]

unused devices: <none>
[4] If a member Disk in RAID array would be failure, re-configure RAID 1 like follows after swapping new Disk.
# the status is like follows in failure

root@dlp:~#
cat /proc/mdstat

Personalities : [raid1]
md0 : active raid1 sdc1[1] sdb1[0]
      83817472 blocks super 1.2 [2/1] [U_]

unused devices: <none>

# after swapping new disk, re-configure like follows

root@dlp:~#
mdadm --manage /dev/md0 --add /dev/sdc1

mdadm: added /dev/sdc1
root@dlp:~#
cat /proc/mdstat

Personalities : [raid1]
md0 : active raid1 sdc1[1] sdb1[0]
      83817472 blocks super 1.2 [2/2] [UU]
      [====>................]  resync = 24.9% (20902592/83817472) finish=7.4min speed=140632K/sec

unused devices: <none>
[5] To use RAID partition, format with a filesystem and mount it on a directory as usual.
# for example, format with ext4 and mount on /mnt

root@dlp:~#
mkfs.ext4 /dev/md0

root@dlp:~#
mount /dev/md0 /mnt

root@dlp:~#
df -hT

Filesystem                  Type      Size  Used Avail Use% Mounted on
udev                        devtmpfs  3.9G     0  3.9G   0% /dev
tmpfs                       tmpfs     794M  612K  794M   1% /run
/dev/mapper/debian--vg-root ext4       77G  1.3G   72G   2% /
tmpfs                       tmpfs     3.9G     0  3.9G   0% /dev/shm
tmpfs                       tmpfs     5.0M     0  5.0M   0% /run/lock
/dev/vda1                   ext2      455M   58M  372M  14% /boot
tmpfs                       tmpfs     794M     0  794M   0% /run/user/0
/dev/md0                    ext4       79G   24K   75G   1% /mnt

# to set in fstab
# because the name of md*** sometimes changes when hardwares are changed, set it with UUID

root@dlp:~#
blkid | grep md

/dev/md0: UUID="b86ccee3-a201-4dee-a44e-f253db4502db" BLOCK_SIZE="4096" TYPE="ext4"

root@dlp:~#
vi /etc/fstab
# set with UUID

/dev/mapper/debian--vg-root /               ext4    errors=remount-ro 0       1
# /boot was on /dev/vda1 during installation
UUID=182de54c-3813-4973-9711-87b5c4f1a7c0 /boot ext2    defaults  0       2
/dev/mapper/debian--vg-swap_1 none            swap    sw              0       0
/dev/disk/by-uuid/b86ccee3-a201-4dee-a44e-f253db4502db /mnt  ext4 defaults 0 0

# that's OK, even if the name of md*** are changed, it is mounted normally

root@dlp:~#
df -hT /mnt

Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/md127     ext4   79G   24K   75G   1% /mnt
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