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I had a drive that was failing on it's SMART test in the form of:

smartctl -a /dev/sdc:

...
# 1  Short offline       Completed: read failure       50%      6354         4377408
# 2  Extended offline    Completed: read failure       90%      6354         4377408

I then wanted to get this 'sector' marked as a bad sector, so I assumed I'd just need to write a load of data on it. So I used dd to write a bunch of zeros. This filled the drive, after which I than ran another smart test.

It completed successfully, however looking at the SMART attributes I don't see any change in:

196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0

Besides knowing full well that I'm always at the risk of a drive failure, is the above information correlated with a drive failure?

Here is diff of the before / after of smartctl's attributes:

diff --git a/x.txt b/x.txt
index 4cfe1b7..1bcace5 100644
--- a/x.txt
+++ b/x.txt
@@ -12,7 +12,7 @@ Sector Sizes:     512 bytes logical, 4096 bytes physical
 Device is:        In smartctl database [for details use: -P show]
 ATA Version is:   ACS-2 (minor revision not indicated)
 SATA Version is:  SATA 3.0, 3.0 Gb/s (current: 3.0 Gb/s)
-Local Time is:    Sun Feb 24 16:50:01 2019 GMT
+Local Time is:    Mon Feb 25 18:33:35 2019 GMT
 SMART support is: Available - device has SMART capability.
 SMART support is: Enabled

@@ -55,31 +55,38 @@ SCT capabilities:          (0x70b5) SCT Status 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   200   200   051    Pre-fail  Always       -       0
-  3 Spin_Up_Time            0x0027   180   179   021    Pre-fail  Always       -       5991
-  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       114
+  1 Raw_Read_Error_Rate     0x002f   200   200   051    Pre-fail  Always       -       4
+  3 Spin_Up_Time            0x0027   177   177   021    Pre-fail  Always       -       6116
+  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       116
   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   092   092   000    Old_age   Always       -       6356
+  9 Power_On_Hours          0x0032   092   092   000    Old_age   Always       -       6372
  10 Spin_Retry_Count        0x0032   100   100   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       -       57
+ 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       59
 192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       46
-193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       67
-194 Temperature_Celsius     0x0022   122   114   000    Old_age   Always       -       28
+193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       69
+194 Temperature_Celsius     0x0022   116   114   000    Old_age   Always       -       34
 196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
 197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
 198 Offline_Uncorrectable   0x0030   100   253   000    Old_age   Offline      -       0
 199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
-200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       1
+200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       0

 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  Short offline       Completed: read failure       50%      6354         4377408
-# 2  Extended offline    Completed: read failure       90%      6354         4377408
+# 1  Extended offline    Completed without error       00%      6367         -
+# 2  Short offline       Completed: read failure       60%      6361         4377409
+# 3  Short offline       Completed: read failure       50%      6361         4377409
+# 4  Extended offline    Completed: read failure       90%      6359         4377409
+# 5  Short offline       Completed without error       00%      6359         -
+# 6  Short offline       Completed: read failure       60%      6356         4377409
+# 7  Short offline       Completed: read failure       50%      6354         4377408
+# 8  Extended offline    Completed: read failure       90%      6354         4377408
+6 of 6 failed self-tests are outdated by newer successful extended offline self-test # 1

 SMART Selective self-test log data structure revision number 1
  SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS

And the current output of smartctl -a:

smartctl 6.6 2018-12-05 r4851 [x86_64-linux-4.14.98] (local build)
Copyright (C) 2002-17, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Western Digital AV-GP (AF)
Device Model:     WDC WD20EURS-63SPKY0
Serial Number:    WD-WMC1T2763021
LU WWN Device Id: 5 0014ee 6addb4b7c
Firmware Version: 80.00A80
User Capacity:    2,000,398,934,016 bytes [2.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 3.0 Gb/s (current: 3.0 Gb/s)
Local Time is:    Mon Feb 25 18:49:12 2019 GMT
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:  (0x00) Offline data collection activity
                    was never started.
                    Auto Offline Data Collection: Disabled.
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:        (27240) 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:    ( 275) minutes.
Conveyance self-test routine
recommended polling time:    (   5) minutes.
SCT capabilities:          (0x70b5) SCT Status 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   200   200   051    Pre-fail  Always       -       4
  3 Spin_Up_Time            0x0027   177   177   021    Pre-fail  Always       -       6116
  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       116
  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   092   092   000    Old_age   Always       -       6373
 10 Spin_Retry_Count        0x0032   100   100   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       -       59
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       46
193 Load_Cycle_Count        0x0032   200   200   000    Old_age   Always       -       69
194 Temperature_Celsius     0x0022   116   114   000    Old_age   Always       -       34
196 Reallocated_Event_Count 0x0032   200   200   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   200   200   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0030   100   253   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x0032   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x0008   200   200   000    Old_age   Offline      -       0

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 without error       00%      6367         -
# 2  Short offline       Completed: read failure       60%      6361         4377409
# 3  Short offline       Completed: read failure       50%      6361         4377409
# 4  Extended offline    Completed: read failure       90%      6359         4377409
# 5  Short offline       Completed without error       00%      6359         -
# 6  Short offline       Completed: read failure       60%      6356         4377409
# 7  Short offline       Completed: read failure       50%      6354         4377408
# 8  Extended offline    Completed: read failure       90%      6354         4377408
6 of 6 failed self-tests are outdated by newer successful extended offline self-test # 1

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.
1

No, you didn't want to mark it as bad sector. You wanted a write op to an unreadable sector :)

As I had quoted yesterday in smartctl reports overall health test as passed but the tests failed?

If the disk can read the sector of data a single time, and the damage is permanent, not transient, then the disk firmware will mark the sector as 'bad' and allocate a spare sector to replace it. But if the disk can't read the sector even once, then it won't reallocate the sector, in hopes of being able, at some time in the future, to read the data from it. A write to an unreadable (corrupted) sector will fix the problem. If the damage is transient, then new consistent data will be written to the sector. If the damange is permanent, then the write will force sector reallocation.

(bold in parts by me, original source: smartmontools FAQ)

There were no reallocated sectors yesterday and there are no reallocated sectors today. That means the disk is in terms of bad sectors "as healthy" as it already was if we ignore the fact that Raw_Read_Error_Rate went up to 4. That was caused by the offline tests?

But you fixed your unreadable sector in tests 1 and 5. That's good. But it's strange that tests 2-4 also failed.

Hmm, maybe I would run the tests a few more times to see what happens. And have an eye on Raw_Read_Error_Rate when you run tests or write zeros with dd.

  • Not sure if it was the cause of the tests but yes Raw_Read_Error_Rate went up after it. Tests 2-4 were done while the write was in process - so it probably never got to that sector by then. Thanks for all your help! – Chris Stryczynski Feb 25 at 21:09

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