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Traditional RAID-5 configurations become increasingly risky as array sizes grow beyond 5TB. The core issue lies in the rebuild process:

# Simplified RAID-5 rebuild pseudocode
def rebuild_raid5(failed_drive, remaining_drives):
    for block in range(total_blocks):
        parity = 0
        for drive in remaining_drives:
            parity ^= drive.read_block(block)
        new_drive.write_block(block, parity)

This XOR-based rebuild requires reading every bit from all surviving drives, creating immense stress during recovery.

ZFS's RAID-Z1 implements several key enhancements:

• Variable stripe width eliminates the "write hole" problem
• Copy-on-write prevents silent corruption
• Checksums enable targeted reconstruction

// ZFS reconstruction logic (simplified)
zfs_reconstruct(device_t *failed, raidz_row_t *row) {
    for (int i = 0; i < row->rr_cols; i++) {
        if (row->rr_col[i].rc_error) {
            raidz_reconstruct(row, i);
            break;
        }
    }
}

For a 5x2TB array, consider these ZFS creation commands:

# Optimal RAID-Z1 pool creation
zpool create tank raidz1 sda sdb sdc sdd sde
zfs set compression=lz4 tank
zfs set atime=off tank

Benchmark results show significant differences:

Regardless of technology:

1. Monitor SMART attributes proactively
2. Maintain proper cooling (below 40°C)
3. Use enterprise-grade drives with TLER
4. Consider RAID-Z2 for arrays >8TB

# SMART monitoring script snippet
smartctl -a /dev/sdX | grep -E "Reallocated|Pending|Uncorrectable"
zpool status -x

RAID-Z1 and RAID-5 both use single parity protection, but their underlying architectures differ significantly. RAID-Z1 implements variable-width stripes (dynamic stripe sizing) that align with ZFS's record sizes, while RAID-5 uses fixed stripe sizes. This becomes crucial during rebuilds:

// RAID-5 traditional fixed stripe
for (block = 0; block < total_blocks; block++) {
    parity = block ^ block ^ block; // Fixed size XOR
}

// RAID-Z1 dynamic stripe (conceptual)
for (transaction = 0; transaction < txg_count; transaction++) {
    parity = adaptive_xor(records_in_transaction); // Variable size
}

The main concern with large arrays isn't just the second failure probability, but Unrecoverable Read Errors (UREs) during rebuild. RAID-Z1 benefits from ZFS's:

• 256-bit checksums for all data and metadata
• Copy-on-write architecture preventing write holes
• Transactional consistency eliminating RAID-5's "silent corruption" risk

Testing on a 4x2TB array shows dramatic differences:

For a 5x2TB array, here's an optimal RAID-Z1 setup:

zpool create tank raidz1 sda sdb sdc sdd sde
zfs set recordsize=1M tank
zfs set compression=lz4 tank
zfs set atime=off tank

The larger recordsize reduces parity overhead and speeds up rebuilds. Compression actually improves performance by reducing I/O operations.

For arrays exceeding 8TB usable space, consider:

• RAID-Z2 (double parity) for better protection
• Hot spares that automatically begin resilvering
• Regular scrubs to detect latent errors:

# Monthly scrub schedule
zpool scrub tank
# Check progress
zpool status -v tank