https://drive.google.com/file/d/1ZlEL7ql-9nvJv-ztb2Y6xKt0dfmVK4xA/view?usp=sharing

1. Understanding RAID-6

Key Concepts

• Striping with Dual Distributed Parity: Data + two parity blocks spread across all disks.
• Fault Tolerance: Survives failure of up to 2 disks simultaneously.
• Capacity: Usable space = (N-2) × smallest disk (e.g., 4×2TB → 4TB usable).
• Minimum Disks: 4 disks required.
• Use Cases:
  • Large storage arrays (>10TB)
  • Archival systems
  • Critical data where rebuild time is long (large disks)
  • Any environment where two-disk failure protection is essential

⚠️ Trade-offs:

• Write penalty: Slower writes (must calculate two parity blocks)
• CPU overhead: Higher than RAID-5 (but negligible on modern systems)

2. Creating RAID-6 Array

Prepare Disks

# Create partitions on 4+ disks (e.g., /dev/sdb-sde)
for disk in sdb sdc sdd sde; do
  sudo fdisk /dev/$disk <<EOF
n
p
1

t
fd
w
EOF
done

sudo partprobe    # Reload partition table
lsblk             # Verify sdb1, sdc1, sdd1, sde1

Create RAID-6

# Create RAID-6 with 4 disks
sudo mdadm --create /dev/md0 -l 6 -n 4 /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1

# Verify
cat /proc/mdstat    # Shows [UUUU] (all disks active)
sudo mdadm -D /dev/md0    # Detailed status (note "Active Devices: 4")

💡 Initial Sync:

RAID-6 initializes dual parity—check /proc/mdstat for [=>...] progress (can take many hours).

Format and Mount

sudo mkfs.ext4 /dev/md0
sudo mkdir /raid6
sudo mount /dev/md0 /raid6
df -hT              # Verify mounted

# Add test data
echo "cal" | sudo tee /raid6/cal
echo "date" | sudo tee /raid6/date