3. RAID Level Commands.md

🖥️ **RAID Level Commands in Linux ** 🖥️

In Linux, RAID (Redundant Array of Independent Disks) is managed using the mdadm (Multiple Disk Administration) tool. Below are the steps and commands to create, manage, and monitor different RAID levels.

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1️⃣ Install mdadm (If Not Installed)

sudo apt install mdadm         # For Debian/Ubuntu
sudo yum install mdadm         # For RHEL/CentOS
sudo dnf install mdadm         # For Fedora

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2️⃣ Check Available Disks

Before setting up RAID, check available disks:

lsblk                             # List all block devices
fdisk -l                          # Show disk partitions

Example output:

sdb     10G  
sdc     10G  
sdd     10G  

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3️⃣ Create Different RAID Levels

🔹 RAID 0 (Striping) - High Performance, No Redundancy

sudo mdadm --create --verbose /dev/md0 --level=0 --raid-devices=2 /dev/sdb /dev/sdc

📌 Example: Combines sdb and sdc into a striped RAID 0 array.

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🔹 RAID 1 (Mirroring) - Data Redundancy

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

📌 Example: Data is mirrored between sdb and sdc.

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🔹 RAID 5 (Striping with Parity) - Performance + Fault Tolerance

sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sdb /dev/sdc /dev/sdd

📌 Example: Stripes data across sdb, sdc, and sdd with parity.

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🔹 RAID 6 (Striping with Dual Parity) - High Fault Tolerance

sudo mdadm --create --verbose /dev/md0 --level=6 --raid-devices=4 /dev/sdb /dev/sdc /dev/sdd /dev/sde

📌 Example: Allows up to two disk failures.

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🔹 RAID 10 (Striping + Mirroring) - Speed + Redundancy

sudo mdadm --create --verbose /dev/md0 --level=10 --raid-devices=4 /dev/sdb /dev/sdc /dev/sdd /dev/sde

📌 Example: Requires a minimum of 4 disks.

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4️⃣ Format and Mount RAID Array

sudo mkfs.ext4 /dev/md0        # Format RAID array
sudo mkdir /mnt/raid           # Create mount directory
sudo mount /dev/md0 /mnt/raid  # Mount RAID array
df -h                          # Verify RAID mount

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5️⃣ Save RAID Configuration

To make RAID persist after reboot:

sudo mdadm --detail --scan >> /etc/mdadm/mdadm.conf
sudo update-initramfs -u          # For Debian/Ubuntu

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6️⃣ Check RAID Status

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

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7️⃣ Stop and Remove RAID

To stop and delete a RAID array:

sudo umount /mnt/raid
sudo mdadm --stop /dev/md0
sudo mdadm --remove /dev/md0
sudo mdadm --zero-superblock /dev/sdb /dev/sdc  # Remove RAID metadata

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