Date

Western Digital HDD Inadequately Writes or Interprets SMART Data. Just a specific case in point to further validate the 2007 Google study that SMART data is unreliable. At work we have a Western Digital Caviar Blue SATA drive that had obviously, at some point, gone bad. If you tried to write or read significant data to the drive you would get I/O errors so it was clear that there are many bad blocks.

So I was curious what the SMART data would show. I was surprised to see SMART saying the drive is still good!

Smart data from the Western Digital Caviar Blue (note the self tests have all failed):

smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.2.0-4-amd64] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF INFORMATION SECTION ===
Model Family:     Western Digital Caviar Blue Serial ATA
Device Model:     WDC WD2500AAKS-00F0A0
Serial Number:    WD-WCAT1E484473
LU WWN Device Id: 5 0014ee 157813d53
Firmware Version: 12.01B02
User Capacity:    250,059,350,016 bytes [250 GB]
Sector Size:      512 bytes logical/physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   8
ATA Standard is:  Exact ATA specification draft version not indicated
Local Time is:    Thu May 23 12:40:47 2013 PDT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

General SMART Values:
Offline data collection status:  (0x82) Offline data collection activity
                    was completed without error.
                    Auto Offline Data Collection: Enabled.
Self-test execution status:      (   0) The previous self-test routine completed
                    without error or no self-test has ever
                    been run.
Total time to complete Offline
data collection:        ( 4680) seconds.
Offline data collection
capabilities:            (0x7b) SMART execute Offline immediate.
                    Auto Offline data collection on/off support.
                    Suspend Offline collection upon new
                    command.
                    Offline surface scan supported.
                    Self-test supported.
                    Conveyance Self-test supported.
                    Selective Self-test supported.
SMART capabilities:            (0x0003) Saves SMART data before entering
                    power-saving mode.
                    Supports SMART auto save timer.
Error logging capability:        (0x01) Error logging supported.
                    General Purpose Logging supported.
Short self-test routine
recommended polling time:    (   2) minutes.
Extended self-test routine
recommended polling time:    (  58) minutes.
Conveyance self-test routine
recommended polling time:    (   5) minutes.
SCT capabilities:          (0x303f) SCT Status supported.
                    SCT Error Recovery Control supported.
                    SCT Feature Control supported.
                    SCT Data Table supported.

SMART Attributes Data Structure revision number: 16
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x002f   192   190   051    Pre-fail  Always       -       116433
  3 Spin_Up_Time            0x0027   201   192   021    Pre-fail  Always       -       950
  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       62
  5 Reallocated_Sector_Ct   0x0033   200   200   140    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x002e   200   200   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   069   069   000    Old_age   Always       -       23002
 10 Spin_Retry_Count        0x0032   100   253   000    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0032   100   253   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       58
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       42
193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       62
194 Temperature_Celsius     0x0022   109   100   000    Old_age   Always       -       34
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   199   165   000    Old_age   Always       -       48
198 Offline_Uncorrectable   0x0030   200   190   000    Old_age   Offline      -       30
199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x0008   183   077   000    Old_age   Offline      -       1754

SMART Error Log Version: 1
No Errors Logged

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Extended offline    Completed: read failure       90%     22177         2016224
# 2  Extended offline    Completed: read failure       90%     22175         18948
# 3  Short offline       Completed: read failure       90%     22175         1859375

SMART Selective self-test log data structure revision number 1
 SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
    1        0        0  Not_testing
    2        0        0  Not_testing
    3        0        0  Not_testing
    4        0        0  Not_testing
    5        0        0  Not_testing
Selective self-test flags (0x0):
  After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.

I wanted to see what it would take to get the SMART controller to fail the drive. So I zeroed the entire disk a couple times. I read the entire drive once or twice. All along the way, the drive threw i/o errors. The result: still PASSED.

According to the linux program badblocks, this drive has 2622 bad blocks. Why is WD's SMART data so unreliable? Clearly when blocks cannot be read or written, the drive has failed. Yet Reallocated_Sector_Ct is zero, which seems to indicate that the firmware does not (or cannot?) reallocate bad sectors.

It's hard to say exactly without knowing more about firmware internals, but it does seem like Western Digital has failed to program their firmware to properly interpret failures and update the SMART database.


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