mdadm is the standard Linux tool for creating and managing software RAID arrays. RAID provides redundancy and/or performance improvements across multiple disks. This guide creates a RAID 1 (mirror) array on Ubuntu 24.04 LTS.

Tested and valid on:

Ubuntu 24.04 LTS

Prerequisites

Ubuntu 24.04 LTS server
Two or more additional block devices (e.g. /dev/sdb, /dev/sdc) of equal size
A user with sudo privileges

Step 1 – Install mdadm

Install the RAID management tool:

sudo apt update
sudo apt install mdadm -y

Step 2 – Identify Available Disks

List available block devices:

lsblk
cat /proc/partitions

Step 3 – Create a RAID 1 Array

Create a mirrored array from /dev/sdb and /dev/sdc:

sudo mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=2 /dev/sdb /dev/sdc

Step 4 – Monitor Array Creation

Watch the synchronisation progress:

cat /proc/mdstat
sudo mdadm --detail /dev/md0

Step 5 – Create a Filesystem and Mount

Format and mount the RAID device:

sudo mkfs.ext4 -F /dev/md0
sudo mkdir /mnt/raid1
sudo mount /dev/md0 /mnt/raid1

Step 6 – Save the Configuration

Save the mdadm config and update initramfs:

sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf
sudo update-initramfs -u

Step 7 – Add to /etc/fstab

Mount automatically on boot:

echo '/dev/md0 /mnt/raid1 ext4 defaults 0 2' | sudo tee -a /etc/fstab

Step 8 – Simulate a Disk Failure

Test RAID resilience by marking a disk as faulty:

sudo mdadm --manage /dev/md0 --fail /dev/sdc
cat /proc/mdstat

Replace the disk:

sudo mdadm --manage /dev/md0 --remove /dev/sdc
sudo mdadm --manage /dev/md0 --add /dev/sdc

Conclusion

Software RAID 1 is now configured on Ubuntu 24.04 LTS with mdadm. Your data is mirrored across two disks — if one fails, the server continues running with no data loss.

How to Set Up Software RAID with mdadm on Ubuntu 24.04