When examining nested RAID configurations, RAID 1+6 demonstrates compelling reliability advantages. For a 16-drive array with 1TB drives, the cumulative probabilities of data loss (per mill) tell a clear story:

RAID 1+0: 0, 67, 200, 385, 590, 776, 910, 980, 1000
RAID 1+5: 0,  0,   0,  15,  77, 217, 441, 702,  910
RAID 1+6: 0,  0,   0,   0,   0,   7,  49, 179,  441

While RAID 1+6 sacrifices 25% storage capacity compared to RAID 1+0 (6TB vs 8TB in 16-drive setup), its theoretical performance metrics remain competitive:

// Pseudo-code for throughput calculation
function calculateThroughput(raidType, driveCount) {
    const singleDriveSpeed = 200; // MB/s
    let writeFactor, readFactor;
    
    switch(raidType) {
        case 'RAID1+0':
            writeFactor = driveCount/2;
            readFactor = driveCount;
            break;
        case 'RAID1+6':
            writeFactor = (driveCount - 2);
            readFactor = driveCount;
            break;
    }
    return {
        write: writeFactor * singleDriveSpeed,
        read: readFactor * singleDriveSpeed
    };
}

During maintenance operations where drives are removed for backups, RAID 1+6 maintains superior reliability compared to triple-mirrored RAID 1+0:

# Python simulation of degraded state probabilities
import math

def combination(n, k):
    return math.factorial(n) // (math.factorial(k) * math.factorial(n-k))

def raid_failure_probability(drives, redundancy):
    total = 0
    for failures in range(redundancy + 1, drives + 1):
        total += combination(drives, failures) * (0.001)**failures
    return total * 1000  # Convert to milli

print(f"RAID1+0 degraded: {raid_failure_probability(8, 2):.1f}‰")
print(f"RAID1+6 degraded: {raid_failure_probability(6, 2):.1f}‰")

The technical hurdles preventing widespread RAID 1+6 adoption include:

• Complexity in controller firmware implementation
• Higher write amplification compared to RAID 10
• Limited support in common storage management tools
• Rebuild times for multiple simultaneous failures

As drive capacities continue to outpace reliability improvements, nested RAID configurations like 1+6 may gain traction. The ability to maintain multiple degraded states while preserving data integrity makes it particularly attractive for:

• Large-scale archival systems
• High-availability financial systems
• Medical imaging storage
• Scientific data repositories

When analyzing nested RAID configurations with 16x1TB drives, RAID 1+6 demonstrates exceptional fault tolerance with only 25% storage overhead compared to RAID 10's 50%. Here's the probability breakdown for data loss scenarios (per milli):

// RAID failure probability comparison
const raid10 = [0, 67, 200, 385, 590, 776, 910, 980, 1000];
const raid15 = [0, 0, 0, 15, 77, 217, 441, 702, 910, 1000];  
const raid16 = [0, 0, 0, 0, 0, 7, 49, 179, 441, 776, 1000];

The theoretical throughput equations reveal why RAID 1+6 isn't universally adopted:

// Throughput calculation pseudocode
function calculateThroughput(raidType, driveCount, slowestDriveSpeed) {
  let writeMultiplier, readMultiplier;
  
  switch(raidType) {
    case '1+0':
      writeMultiplier = driveCount/2;
      readMultiplier = driveCount;
      break;
    case '1+6':
      writeMultiplier = (driveCount/2) - 2; 
      readMultiplier = driveCount;
      break;
  }
  return {
    write: writeMultiplier * slowestDriveSpeed,
    read: readMultiplier * slowestDriveSpeed
  };
}

While RAID 1+6 offers better protection during normal operation, its rebuild characteristics create operational challenges:

• RAID 10 rebuilds involve simple mirror copies (1:1 data transfer)
• RAID 1+6 requires parity recalculations across multiple drives
• During rebuilds, RAID 1+6 performs 6-8× more I/O operations than RAID 10

Most hardware RAID controllers optimize for either mirroring or parity schemes, not both. Here's a Linux mdadm configuration example showing the complexity:

# RAID 1+6 implementation steps
# Step 1: Create mirrored pairs
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-devices=2 /dev/sdc1 /dev/sdd1
[... repeat for all pairs ...]

# Step 2: Combine into RAID6
mdadm --create /dev/md10 --level=6 --raid-devices=8 \\
  /dev/md0 /dev/md1 /dev/md2 /dev/md3 /dev/md4 /dev/md5 /dev/md6 /dev/md7

Emerging technologies might make RAID 1+6 more practical:

1. Zoned Namespace (ZNS) SSDs reducing rebuild impact
2. Computational storage offloading parity calculations
3. Machine learning predicting drive failures

The storage industry continues evolving, and RAID 1+6 may find niche applications where its reliability advantages outweigh the performance tradeoffs.