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.