https://drive.google.com/file/d/1TCl2Gx_DEuQJB2IZ5fzlUF5LlygotjMu/view?usp=sharing

1. Understanding RAID-1

Key Concepts

• Mirroring: Data is duplicated across all disks in the array.
• Fault Tolerance: Survives failure of 1 disk (in a 2-disk setup).
• Capacity: Usable space = size of smallest disk (50% efficiency for 2 disks).
• Use Cases:
  • Critical system disks (/, /boot)
  • Database servers
  • Any workload requiring high availability

✅ RAID-1 Benefit:

Read performance ≈ 2x single disk (can read from both disks simultaneously).

Write performance ≈ single disk (must write to both disks).

2. Creating RAID-1 Array

Prepare Disks

# Create partitions on 2 disks (e.g., /dev/sdb, /dev/sdc)
sudo fdisk /dev/sdb
# Commands: n → p → 1 → [Enter] → [Enter] → t → fd (Linux RAID) → w

sudo fdisk /dev/sdc
# Same steps → /dev/sdc1

sudo partprobe    # Reload partition table
lsblk             # Verify sdb1, sdc1

Create RAID-1

# Create mirror with 2 disks
sudo mdadm -C /dev/md0 -l 1 -n 2 /dev/sdb1 /dev/sdc1

# Verify
cat /proc/mdstat    # Shows [UU] (both disks active)
sudo mdadm -D /dev/md0    # Detailed status
lsblk -f            # Shows /dev/md0

💡 Note:

Initial sync may take time (check /proc/mdstat for [=>...] progress).

Format and Mount

sudo mkfs.ext4 /dev/md0
sudo mkdir /raid1
sudo mount /dev/md0 /raid1
df -hT              # Verify mounted

# Add test data
echo "cal" | sudo tee /raid1/cal
echo "date" | sudo tee /raid1/date

3. Simulating Disk Failure