When your Western Digital VelociRaptor (WD3000HLFS-01G6U0) reports UNC (Uncorrectable Error) in S.M.A.R.T. attributes, it indicates the drive failed to read data from sector LBA 0x0053cb44 (5491524 in decimal) after multiple attempts. This is serious because:

• The drive logged 749 ATA errors (showing last 5 instances)
• Offline_Uncorrectable count shows 4 bad sectors
• Error persists across multiple read attempts (FPDMA QUEUED commands)

Analyzing the smartctl output reveals critical details:

# Key problematic attributes:
198 Offline_Uncorrectable   0x0010   200   200   000    Old_age   Offline      -       4
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       1

The drive has 10,292 power-on hours (~1.2 years continuous operation). While Reallocated_Sector_Ct is 0, UNC errors often precede physical sector failures.

For programmers managing multiple drives, here's a Python monitoring script using smartmontools:

import subprocess
import json

def check_smart_errors(device):
    cmd = f"smartctl -a {device} --json"
    result = subprocess.run(cmd.split(), capture_output=True, text=True)
    
    if result.returncode != 0:
        return {"error": "SMART command failed"}
    
    data = json.loads(result.stdout)
    
    critical_errors = {
        'unc_errors': data.get('ata_smart_error_log', {}).get('summary', {}).get('count', 0),
        'offline_uncorrectable': next(
            (item['raw']['value'] for item in data['ata_smart_attributes']['table'] 
             if item['name'] == 'Offline_Uncorrectable'), None)
    }
    
    return critical_errors

# Example usage
print(check_smart_errors("/dev/sda"))

For a WD Raptor showing these symptoms:

1. Backup immediately: Use ddrescue to clone the drive:

   ddrescue -f -n /dev/sdX /path/to/backup.img /path/to/logfile.log

2. Run extended self-test:

   smartctl -t long /dev/sdX

3. Check warranty status using WD's tools:

   warranty-check --serial WD-WXD0C79C8807

For systems programmers needing to work around bad sectors:

# Linux: Mark bad sector as unusable
hdparm --read-sector 5491524 /dev/sdX  # Verify
hdparm --write-sector 5491524 /dev/sdX  # Force reallocation

# Windows (PowerShell):
Get-Disk | Where Model -like "*WD3000HLFS*" | 
Initialize-Disk -PartitionStyle GPT -Confirm:$false

WD's criteria for RMA typically requires:

• Reallocated sectors > threshold (usually 50-100)
• Pending sectors that persist after reformat
• UNC errors affecting system stability

Your drive shows early warning signs. While it may still pass SMART overall-health, the UNC errors and 4 offline uncorrectable sectors warrant replacement under most enterprise support contracts.

---

Your WD3000HLFS-01G6U0 VelociRaptor drive is showing Error: UNC at LBA = 0x0053cb44 = 5491524 in SMART logs. UNC (Uncorrectable Error) means the drive's error correction couldn't recover data from sector 5491524 after multiple retries. This is concerning because:

• The error persists across multiple read attempts (visible in the 5 logged instances)
• Offline_Uncorrectable shows RAW_VALUE=4
• Total ATA Error Count=749 indicates historical issues

While the drive shows SMART overall-health self-assessment test result: PASSED, these values deserve attention:

ID# ATTRIBUTE_NAME          VALUE WORST THRESH RAW_VALUE
  5 Reallocated_Sector_Ct   200   200   140    0
197 Current_Pending_Sector  200   200   0      0
198 Offline_Uncorrectable   200   200   0      4
200 Multi_Zone_Error_Rate   200   200   0      1

Key observations:

1. No reallocated sectors yet (good sign)

2. But 4 uncorrectable sectors exist

3. Power_On_Hours=10292 (≈428 days) suggests moderate usage

1. Verify the bad sector:

# Use dd to test specific LBA
dd if=/dev/sdX skip=5491524 count=1 bs=512 2>&1 | grep -v "records"

2. Check filesystem integrity:

# For NTFS
chkdsk /f X:

# For ext4
fsck -v /dev/sdX1

3. Run extended SMART test:

smartctl -t long /dev/sdX
smartctl -l selftest /dev/sdX

For critical data at the bad sector:

# GNU ddrescue approach
ddrescue -b 512 -r 3 -v /dev/sdX recovered.img recovery.log

# Alternative with badblocks
badblocks -sv -b 512 -o bad.txt /dev/sdX 5491524 5491524

Western Digital's warranty typically covers drives with UNC errors:

• Check warranty status: smartctl -i /dev/sdX | grep -i warranty
• VelociRaptor series usually has 5-year warranty
• Prepare SMART full report: smartctl -x /dev/sdX > wd_claim.txt

Create a Python monitoring script (save as smart_monitor.py):

import subprocess
import json

def check_smart(device):
    cmd = f"smartctl -j -a {device}"
    try:
        output = subprocess.check_output(cmd.split()).decode()
        data = json.loads(output)
        
        print(f"Device: {data['model_name']} (S/N: {data['serial_number']})")
        print(f"Power On Hours: {data['power_on_time']['hours']}")
        
        if data['ata_smart_error_log']['summary']['count'] > 0:
            print(f"\nWARNING: {data['ata_smart_error_log']['summary']['count']} ATA errors!")
            for error in data['ata_smart_error_log']['table'][:3]:
                print(f"LBA: {error['lba']}, Error: {error['error_description']}")
        
        if data['ata_smart_data']['offline_data_collection']['status']['string'] != "completed without error":
            print("\nRecommend running extended SMART test")

    except Exception as e:
        print(f"Error checking {device}: {str(e)}")

check_smart("/dev/sdX")

Consider RMA if:

• Extended SMART test fails
• Uncorrectable errors increase over time
• System logs show repeated I/O errors
• Critical data resides in affected sectors