Difference between revisions of "Basic usage of Software Raid (MDADM)"
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(Created page with "== Creating and Using Software RAID with mdadm on Debian == Software RAID on Debian is commonly configured using the <code>mdadm</code> utility. This guide provides a step-by...") |
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Install the RAID management tool: | Install the RAID management tool: | ||
| − | + | ||
| − | sudo apt update | + | sudo apt update |
| − | sudo apt install mdadm -y | + | sudo apt install mdadm -y |
| − | + | ||
During installation, you may be prompted to configure mdadm to email alerts. You can skip or configure as preferred. | During installation, you may be prompted to configure mdadm to email alerts. You can skip or configure as preferred. | ||
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List all attached storage devices: | List all attached storage devices: | ||
| − | + | ||
| − | lsblk | + | lsblk |
| − | + | ||
Or use: | Or use: | ||
| − | + | ||
| − | sudo fdisk -l | + | sudo fdisk -l |
| − | + | ||
Ensure the devices are **unmounted** and **do not contain any important data**. | Ensure the devices are **unmounted** and **do not contain any important data**. | ||
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==== RAID 1 (Mirroring, 2 Disks) ==== | ==== RAID 1 (Mirroring, 2 Disks) ==== | ||
| − | + | ||
| − | sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc | + | sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc |
| − | + | ||
==== RAID 0 (Striping, 2+ Disks) ==== | ==== RAID 0 (Striping, 2+ Disks) ==== | ||
| − | + | ||
| − | sudo mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc | + | sudo mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc |
| − | + | ||
==== RAID 5 (Striped with Parity, 3+ Disks) ==== | ==== RAID 5 (Striped with Parity, 3+ Disks) ==== | ||
| − | + | ||
| − | sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd | + | sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd |
| − | + | ||
You may need to confirm with '''yes''' to proceed. | You may need to confirm with '''yes''' to proceed. | ||
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Check array status: | Check array status: | ||
| − | + | ||
| − | cat /proc/mdstat | + | cat /proc/mdstat |
| − | + | ||
To view detailed status: | To view detailed status: | ||
| − | + | ||
| − | sudo mdadm --detail /dev/md0 | + | sudo mdadm --detail /dev/md0 |
| − | + | ||
=== Step 5: Create Filesystem on RAID Array === | === Step 5: Create Filesystem on RAID Array === | ||
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After creation completes, format the RAID array: | After creation completes, format the RAID array: | ||
| − | + | ||
| − | sudo mkfs.ext4 /dev/md0 | + | sudo mkfs.ext4 /dev/md0 |
| − | + | ||
=== Step 6: Mount the RAID Array === | === Step 6: Mount the RAID Array === | ||
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Create mount point and mount it: | Create mount point and mount it: | ||
| − | + | ||
| − | sudo mkdir /mnt/raid | + | sudo mkdir /mnt/raid |
| − | sudo mount /dev/md0 /mnt/raid | + | sudo mount /dev/md0 /mnt/raid |
| − | + | ||
Optional: Set up ownership or permissions: | Optional: Set up ownership or permissions: | ||
| − | + | ||
| − | sudo chown user:user /mnt/raid | + | sudo chown user:user /mnt/raid |
| − | + | ||
=== Step 7: Save mdadm Configuration === | === Step 7: Save mdadm Configuration === | ||
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Save the array details for boot persistence: | Save the array details for boot persistence: | ||
| − | + | ||
| − | sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf | + | sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf |
| − | sudo update-initramfs -u | + | sudo update-initramfs -u |
| − | + | ||
=== Step 8: Automount on Boot === | === Step 8: Automount on Boot === | ||
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Add entry to <code>/etc/fstab</code>: | Add entry to <code>/etc/fstab</code>: | ||
| − | + | ||
| − | sudo nano /etc/fstab | + | sudo nano /etc/fstab |
| − | + | ||
Add: | Add: | ||
| − | + | ||
| − | /dev/md0 /mnt/raid ext4 defaults,nofail 0 0 | + | /dev/md0 /mnt/raid ext4 defaults,nofail 0 0 |
| − | + | ||
Save and close. | Save and close. | ||
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If RAID is not automatically detected: | If RAID is not automatically detected: | ||
| − | + | ||
| − | sudo mdadm --assemble --scan | + | sudo mdadm --assemble --scan |
| − | + | ||
=== Optional: Remove or Stop a RAID Array === | === Optional: Remove or Stop a RAID Array === | ||
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To stop the array: | To stop the array: | ||
| − | + | ||
| − | sudo umount /mnt/raid | + | sudo umount /mnt/raid |
| − | sudo mdadm --stop /dev/md0 | + | sudo mdadm --stop /dev/md0 |
| − | + | ||
To remove the array: | To remove the array: | ||
| − | + | ||
| − | sudo mdadm --remove /dev/md0 | + | sudo mdadm --remove /dev/md0 |
| − | + | ||
To zero out superblocks: | To zero out superblocks: | ||
| − | + | ||
| − | sudo mdadm --zero-superblock /dev/sdb | + | sudo mdadm --zero-superblock /dev/sdb |
| − | sudo mdadm --zero-superblock /dev/sdc | + | sudo mdadm --zero-superblock /dev/sdc |
| − | + | ||
=== Summary Table === | === Summary Table === | ||
Latest revision as of 14:17, 19 May 2025
Contents
- 1 Creating and Using Software RAID with mdadm on Debian
- 1.1 Prerequisites
- 1.2 Step 1: Install mdadm
- 1.3 Step 2: Identify Available Disks
- 1.4 Step 3: Create the RAID Array
- 1.5 Step 4: Monitor the RAID Creation
- 1.6 Step 5: Create Filesystem on RAID Array
- 1.7 Step 6: Mount the RAID Array
- 1.8 Step 7: Save mdadm Configuration
- 1.9 Step 8: Automount on Boot
- 1.10 Optional: Assemble RAID After Reboot
- 1.11 Optional: Remove or Stop a RAID Array
- 1.12 Summary Table
- 1.13 See Also
Creating and Using Software RAID with mdadm on Debian
Software RAID on Debian is commonly configured using the mdadm utility. This guide provides a step-by-step approach for creating, configuring, and managing a basic RAID array (RAID 0, RAID 1, or RAID 5), suitable for both virtual and dedicated servers.
Prerequisites
- Two or more storage devices (e.g., /dev/sdb, /dev/sdc)
- Root or sudo privileges
- Debian 10, 11, 12 or Ubuntu derivative
- Non-mounted and unformatted target disks
Step 1: Install mdadm
Install the RAID management tool:
sudo apt update sudo apt install mdadm -y
During installation, you may be prompted to configure mdadm to email alerts. You can skip or configure as preferred.
Step 2: Identify Available Disks
List all attached storage devices:
lsblk
Or use:
sudo fdisk -l
Ensure the devices are **unmounted** and **do not contain any important data**.
Step 3: Create the RAID Array
Examples:
RAID 1 (Mirroring, 2 Disks)
sudo mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
RAID 0 (Striping, 2+ Disks)
sudo mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc
RAID 5 (Striped with Parity, 3+ Disks)
sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd
You may need to confirm with yes to proceed.
Step 4: Monitor the RAID Creation
Check array status:
cat /proc/mdstat
To view detailed status:
sudo mdadm --detail /dev/md0
Step 5: Create Filesystem on RAID Array
After creation completes, format the RAID array:
sudo mkfs.ext4 /dev/md0
Step 6: Mount the RAID Array
Create mount point and mount it:
sudo mkdir /mnt/raid sudo mount /dev/md0 /mnt/raid
Optional: Set up ownership or permissions:
sudo chown user:user /mnt/raid
Step 7: Save mdadm Configuration
Save the array details for boot persistence:
sudo mdadm --detail --scan | sudo tee -a /etc/mdadm/mdadm.conf sudo update-initramfs -u
Step 8: Automount on Boot
Add entry to /etc/fstab:
sudo nano /etc/fstab
Add:
/dev/md0 /mnt/raid ext4 defaults,nofail 0 0
Save and close.
Optional: Assemble RAID After Reboot
If RAID is not automatically detected:
sudo mdadm --assemble --scan
Optional: Remove or Stop a RAID Array
To stop the array:
sudo umount /mnt/raid sudo mdadm --stop /dev/md0
To remove the array:
sudo mdadm --remove /dev/md0
To zero out superblocks:
sudo mdadm --zero-superblock /dev/sdb sudo mdadm --zero-superblock /dev/sdc
Summary Table
| Task | Command | Description |
|---|---|---|
| Install mdadm | apt install mdadm |
Install RAID tool |
| Create RAID 1 | mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdX /dev/sdY |
Create mirrored array |
| Monitor RAID | cat /proc/mdstat |
View sync/progress |
| Format array | mkfs.ext4 /dev/md0 |
Prepare filesystem |
| Mount array | mount /dev/md0 /mnt/raid |
Use RAID volume |
| Auto-mount | /etc/fstab |
Persistent configuration |
| Save config | mdadm --detail --scan >> /etc/mdadm/mdadm.conf |
Boot-time detection |
