those two disks should become one md0 RAID1 mirroring array…

# list installed block devices
root@Microknoppix:/# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931,5G  0 disk
└─sda1   8:1    0 931,5G  0 part
sdb      8:16   0   1,8T  0 disk
sdc      8:32   0  29,8G  0 disk
├─sdc1   8:33   0     1G  0 part [SWAP]
└─sdc2   8:34   0  28,8G  0 part /
sdd      8:48   0   1,8T  0 disk
sr0     11:0    1  1024M  0 rom
sr1     11:1    1  1024M  0 rom
zram0  251:0    0   2,6G  0 disk [SWAP]

# start partitioning the first disk
fdisk /dev/sdb
# create new primary partition
p (hit enter, enter, enter to use the full disk as one big partition)
t (hit t then enter: fd followed by enter to label the partition "linux raid autodetect")
w (hit w to write changes to disk)

# ... do the same with sdd

# create the raid1 array containing the two partitions
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdd1

# sample output:
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.

# now you have an new device md0 that represents your raid1-array

# lets format this new array
mkfs.ext4 /dev/md0

# it's a good idea to give it a meaningful label
e2label /dev/md0 "RAID1DATA"

Add entry to fstab:

/dev/md0 /home ext3 noatime,rw 0 0

Create mdadm config file:


# test config output
root@Microknoppix:/home/knoppix# mdadm --examine --scan
ARRAY /dev/md/0 metadata=1.2 UUID=53ca5f4e:c16a6706:a216c510:5122e016 name=Microknoppix:0

# save config output to config file
root@Microknoppix:/home/knoppix# mdadm --examine --scan >> /etc/mdadm/mdadm.conf

Note that the array is actually started in /etc/rc0.d/K13mdadm-raid (via mdadm -A -s) or mdrun command

# test what would happen on reboot
/etc/rc0.d/K13mdadm-raid start

# sample output
[ ok ] Assembling MD array md0...done (started [2/2]).
[ ok ] Generating udev events for MD arrays...done.

# to watch your raids at work
watch -n 2 cat /proc/mdstat

source: https://wiki.debian.org/SoftwareRAID

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