Simple (Non-System) Raid 1 Setup in Ubuntu Using MDADM

I had trouble finding tutorials on setting up a simple filesystem raid 1 setup. Most were geared towards setting up Ubuntu on a Raid 1 array.

List your disks:

$ sudo fdisk -l

This will give an output like:

Disk /dev/sdd: 240.1 GB, 240057409536 bytes
81 heads, 63 sectors/track, 91879 cylinders, total 468862128 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x211bbf32

Device Boot Start End Blocks Id System
/dev/sdd1 2048 468862127 234430040 fd Linux raid autodetect

Disk /dev/sde: 240.1 GB, 240057409536 bytes
81 heads, 63 sectors/track, 91879 cylinders, total 468862128 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x22e6d1f2

Device Boot Start End Blocks Id System
/dev/sde1 2048 468862127 234430040 fd Linux raid autodetect

The two disks that I listed above have already been added to an array, but the output should be roughly similar (yours won’t she partitions). The two devices I’ll be working with are /dev/sdd and /dev/sde.

Now, we are ready to begin creating our array:

$ sudo fdisk /dev/sdd

Press the following keys:

  1. n for new partition, then
  2. p for primary, then
  3. 1 for partition 1, then
  4. enter & enter again.

You’ll want to change the system id, so press “t” and then type “FD.” FD is the hex code to designate it as Linux Raid Autodetect.

  1. Press “w” to write changes.

Repeat the above steps for your second drive (/dev/sde in my case).

Now, we are ready to run mdadm (if you haven’t already, type in sudo apt-get install mdadm)

$ sudo mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdd1 /dev/sde1

While it’s creating the array, you can watch the process with:

$ watch cat /proc/mdstat

Once it’s done creating the array, we’ll need to create a filesystem on the drive:

$ sudo mkfs -t ext4 /dev/md0

After that, we’ll want to mount the array somewhere, I chose /raid

$ sudo mkdir /raid

$ sudo mount /dev/md0 /raid

To permanently mount it, you’ll want to mount it by UUID, so type in:

$ sudo blkid

Fine the output that looks like:

/dev/md0: LABEL="KVM" UUID="758f8408-caed-49dc-98f9-xxxxxxxxx" TYPE="ext4"
$ sudo nano /etc/fstab
UUID=758f8408-caed-49dc-98f9-xxxxxxxx /raid auto defaults 0 0

That’s pretty much it!

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