Software RAID with mdadm provides data redundancy and performance improvements using standard hardware without a dedicated RAID controller. RAID 1 (mirroring) protects against single disk failure, while RAID 5 and 6 provide space efficiency with fault tolerance. This guide creates a RAID 1 array on Ubuntu 26.04 LTS.

Tested and valid on:

  • Ubuntu 26.04 LTS

Prerequisites

  • Ubuntu 26.04 LTS
  • Two or more identical physical disks
  • A user with sudo privileges

Step 1 – Install mdadm

sudo apt update
sudo apt install mdadm -y

Step 2 – Identify the Disks

sudo lsblk
sudo fdisk -l | grep -E '^Disk'

Step 3 – Create a RAID 1 Array

Using /dev/sdb and /dev/sdc as an example:

sudo mdadm --create --verbose /dev/md0 
  --level=1 
  --raid-devices=2 
  /dev/sdb /dev/sdc
cat /proc/mdstat

Step 4 – Format and Mount the Array

sudo mkfs.ext4 /dev/md0
sudo mkdir -p /mnt/raid1
sudo mount /dev/md0 /mnt/raid1
df -h /mnt/raid1

Step 5 – Configure Persistent Mount

sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf
sudo update-initramfs -u
echo '/dev/md0 /mnt/raid1 ext4 defaults 0 2' | sudo tee -a /etc/fstab

Step 6 – Monitor RAID Status

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

Step 7 – Simulate Disk Failure and Recovery

# Mark a disk as failed:
sudo mdadm /dev/md0 --fail /dev/sdb
# Remove the failed disk:
sudo mdadm /dev/md0 --remove /dev/sdb
# Add a replacement disk:
sudo mdadm /dev/md0 --add /dev/sdd
# Watch rebuild:
watch cat /proc/mdstat

Conclusion

Software RAID 1 is configured with mdadm on Ubuntu 26.04 LTS. Your data is now mirrored across two disks. Configure email alerts in /etc/mdadm/mdadm.conf so you are notified immediately if a disk fails.