# Is my disk dying?

## Olis

Hi everybody,

two days ago smartd sent me an email:

```
The following warning/error was logged by the smartd daemon:

Device: /dev/sda [SAT], 1 Currently unreadable (pending) sectors
```

So I ran a long selftest on /dev/sda. I'm doing the long selftest  weekly and never saw any problems. Same today...

```
 ~ # smartctl -a /dev/sda

smartctl 5.40 2010-10-16 r3189 [i686-pc-linux-gnu] (local build)

Copyright (C) 2002-10 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF INFORMATION SECTION ===

Model Family:     SAMSUNG SpinPoint T166 series

Device Model:     SAMSUNG HD501LJ

Serial Number:    S10NJ1KP714345

Firmware Version: CR100-10

User Capacity:    500,107,862,016 bytes

Device is:        In smartctl database [for details use: -P show]

ATA Version is:   8

ATA Standard is:  ATA-8-ACS revision 3b

Local Time is:    Sat Apr  9 16:27:15 2011 CEST

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:                 (9114) seconds.

Offline data collection

capabilities:                    (0x5b) SMART execute Offline immediate.

                                        Auto Offline data collection on/off support.

                                        Suspend Offline collection upon new

                                        command.

                                        Offline surface scan supported.

                                        Self-test supported.

                                        No 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:        ( 155) minutes.

SCT capabilities:              (0x003f) 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     0x000f   100   100   051    Pre-fail  Always       -       9

  3 Spin_Up_Time            0x0007   100   100   015    Pre-fail  Always       -       7552

  4 Start_Stop_Count        0x0032   100   100   000    Old_age   Always       -       128

  5 Reallocated_Sector_Ct   0x0033   253   253   010    Pre-fail  Always       -       0

  7 Seek_Error_Rate         0x000f   253   253   051    Pre-fail  Always       -       0

  8 Seek_Time_Performance   0x0025   253   253   015    Pre-fail  Offline      -       0

  9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       30708

 10 Spin_Retry_Count        0x0033   253   253   051    Pre-fail  Always       -       0

 11 Calibration_Retry_Count 0x0012   253   100   000    Old_age   Always       -       0

 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       103

187 Reported_Uncorrect      0x0032   253   253   000    Old_age   Always       -       655360

188 Command_Timeout         0x0032   253   253   000    Old_age   Always       -       0

190 Airflow_Temperature_Cel 0x0022   064   055   000    Old_age   Always       -       36

194 Temperature_Celsius     0x0022   130   103   000    Old_age   Always       -       36

195 Hardware_ECC_Recovered  0x001a   100   100   000    Old_age   Always       -       840177878

196 Reallocated_Event_Count 0x0032   253   253   000    Old_age   Always       -       0

197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       1

198 Offline_Uncorrectable   0x0030   253   253   000    Old_age   Offline      -       0

199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -       0

200 Multi_Zone_Error_Rate   0x000a   100   100   000    Old_age   Always       -       0

201 Soft_Read_Error_Rate    0x000a   100   100   000    Old_age   Always       -       0

202 Data_Address_Mark_Errs  0x0032   253   253   000    Old_age   Always       -       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%     30700         -

# 2  Short offline       Completed without error       00%     30675         -

# 3  Extended offline    Completed without error       00%     30539         -

# 4  Extended offline    Completed without error       00%     30367         -

# 5  Extended offline    Completed without error       00%     30198         -

# 6  Extended offline    Completed without error       00%     30029         -

# 7  Extended offline    Completed without error       00%     29863         -

# 8  Extended offline    Completed without error       00%     29701         -

# 9  Extended offline    Completed without error       00%     29525         -

#10  Extended offline    Completed without error       00%     29357         -

#11  Extended offline    Completed without error       00%     29189         -

#12  Extended offline    Completed without error       00%     29021         -

#13  Extended offline    Completed without error       00%     28853         -

#14  Extended offline    Completed without error       00%     28685         -

#15  Extended offline    Completed without error       00%     28516         -

#16  Extended offline    Completed without error       00%     28349         -

#17  Extended offline    Completed without error       00%     28182         -

#18  Extended offline    Completed without error       00%     28031         -

#19  Extended offline    Completed without error       00%     27844         -

#20  Extended offline    Completed without error       00%     27677         -

#21  Extended offline    Completed without error       00%     27509         -

Note: selective self-test log revision number (0) not 1 implies that no selective self-test has ever been run

SMART Selective self-test log data structure revision number 0

Note: revision number not 1 implies that no selective self-test has ever been run

 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 also ran "badblocks -s -c 256 /dev/sda" but again it found no problems.

Nevertheless the smartmon daemon is logging 1 unreadable sector every half an hour.

```
Apr  9 17:22:35 frodo smartd[8608]: Device: /dev/sda [SAT], 1 Currently unreadable (pending) sectors

Apr  9 17:52:35 frodo smartd[8608]: Device: /dev/sda [SAT], 1 Currently unreadable (pending) sectors

Apr  9 18:22:35 frodo smartd[8608]: Device: /dev/sda [SAT], 1 Currently unreadable (pending) sectors

Apr  9 18:52:35 frodo smartd[8608]: Device: /dev/sda [SAT], 1 Currently unreadable (pending) sectors
```

I think I will replace the drive since the data on it is much more expensive than a new drive. Nevertheless I'm asking myself if there's really a problem with my drive.

Oliver

----------

## Hypnos

 *Olis wrote:*   

> I think I will replace the drive since the data on it is much more expensive than a new drive.

 

So this means you have a full backup on another disk, right?

As for your question, I don't know either, since all your tools report everything OK.  It may be that your hard disk controller is running a check that your generic Linux software does not/cannot, and you should use the manufacturer's specialized software tools to investigate further.  In any event, I agree that it's wise to replace the disk.

----------

## Olis

 *Hypnos wrote:*   

>  *Olis wrote:*   I think I will replace the drive since the data on it is much more expensive than a new drive. 
> 
> So this means you have a full backup on another disk, right?
> 
> As for your question, I don't know either, since all your tools report everything OK.  It may be that your hard disk controller is running a check that your generic Linux software does not/cannot, and you should use the manufacturer's specialized software tools to investigate further.  In any event, I agree that it's wise to replace the disk.

 

Yes, I have a full backup on another disk and I have the same model as a replacement.

I was just wondering why smartmontools report an unreadable error, while the same tool doesn't find a defective block during the long selftest.

badblocks reads the whole disk sector by sector. And it also didn't find a problem. So I mirrored the (probably) defective disk using dd to my spare disk and then replaced it. The replacement disk is now running fine and smartd doesn't report any errors.

----------

## Hypnos

If you're curious, try the tools directly from the hard disk manufacturer, see if that can catch anything.

----------

## Mad Merlin

Disks reserve a small number of sectors for remapping bad sectors. Next time you write to that sector, it will be transparently remapped to a different sector and no errors will be reported back to the host OS. Eventually, you'll run out of extra sectors, and you'll want to replace the disk before that time, but a single bad sector is generally nothing to worry about. When the number starts rising steadily, it's time to chuck the drive. Don't count on having more than a few dozen reserved sectors though.

----------

