I have an external SSD that suffered some file corruption earlier this week. Model is

Model Family:     Crucial/Micron RealSSD m4/C400/P400
Device Model:     M4-CT256M4SSD2

with, apparently, 20,000 power on hours on the clock.

Even though the status is:

SMART overall-health self-assessment test result: PASSED

the self-testing is failing:

enter image description here

gsmartcontrol reports the attributes as:

enter image description here

Full output is:

smartctl 7.2 2020-12-30 r5155 [x86_64-w64-mingw32-w10-b19045] (sf-7.2-1)
Copyright (C) 2002-20, Bruce Allen, Christian Franke, www.smartmontools.org

Model Family:     Crucial/Micron RealSSD m4/C400/P400
Device Model:     M4-CT256M4SSD2
Serial Number:    0000000012050904896A
LU WWN Device Id: 5 00a075 10904896a
Firmware Version: 0309
User Capacity:    256,060,514,304 bytes [256 GB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    Solid State Device
Form Factor:      2.5 inches
TRIM Command:     Available, deterministic
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2, ATA8-ACS T13/1699-D revision 6
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Wed Apr 05 11:36:29 2023 PM
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
AAM feature is:   Unavailable
APM level is:     254 (maximum performance)
Rd look-ahead is: Enabled
Write cache is:   Enabled
DSN feature is:   Unavailable
ATA Security is:  Disabled, NOT FROZEN [SEC1]

SMART Status not supported: Incomplete response, ATA output registers missing
SMART overall-health self-assessment test result: PASSED
Warning: This result is based on an Attribute check.

General SMART Values:
Offline data collection status:  (0x80) Offline data collection activity
                    was never started.
                    Auto Offline Data Collection: Enabled.
Self-test execution status:      ( 117) The previous self-test completed having
                    the read element of the test failed.
Total time to complete Offline 
data collection:        ( 1190) seconds.
Offline data collection
capabilities:            (0x7b) SMART execute Offline immediate.
                    Auto Offline data collection on/off support.
                    Suspend Offline collection upon new
                    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:    (  19) minutes.
Conveyance self-test routine
recommended polling time:    (   3) minutes.
SCT capabilities:          (0x003d) 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:
  1 Raw_Read_Error_Rate     POSR-K   100   100   050    -    0
  5 Reallocated_Sector_Ct   PO--CK   099   099   010    -    36864 (0 5)
  9 Power_On_Hours          -O--CK   100   100   001    -    19434
 12 Power_Cycle_Count       -O--CK   100   100   001    -    626
170 Grown_Failing_Block_Ct  PO--CK   099   099   010    -    89
171 Program_Fail_Count      -O--CK   100   100   001    -    20
172 Erase_Fail_Count        -O--CK   100   100   001    -    64
173 Wear_Leveling_Count     PO--CK   083   083   010    -    524
174 Unexpect_Power_Loss_Ct  -O--CK   100   100   001    -    5
181 Non4k_Aligned_Access    -O---K   100   100   001    -    9248 4153 5094
183 SATA_Iface_Downshift    -O--CK   100   100   001    -    0
184 End-to-End_Error        PO--CK   100   100   050    -    0
187 Reported_Uncorrect      -O--CK   100   100   001    -    582
188 Command_Timeout         -O--CK   100   100   001    -    0
189 Factory_Bad_Block_Ct    -OSR--   100   100   001    -    85
194 Temperature_Celsius     -O---K   100   100   000    -    0
195 Hardware_ECC_Recovered  -O-RCK   100   100   001    -    353
196 Reallocated_Event_Count -O--CK   100   100   001    -    89
197 Current_Pending_Sector  -O--CK   100   100   001    -    0
198 Offline_Uncorrectable   ----CK   100   100   001    -    0
199 UDMA_CRC_Error_Count    -O--CK   100   100   001    -    3
202 Perc_Rated_Life_Used    ---RC-   083   083   001    -    17
206 Write_Error_Rate        -OSR--   100   100   001    -    20
                            ||||||_ K auto-keep
                            |||||__ C event count
                            ||||___ R error rate
                            |||____ S speed/performance
                            ||_____ O updated online
                            |______ P prefailure warning

General Purpose Log Directory Version 1
SMART           Log Directory Version 1 [multi-sector log support]
Address    Access  R/W   Size  Description
0x00       GPL,SL  R/O      1  Log Directory
0x01           SL  R/O      1  Summary SMART error log
0x02           SL  R/O     51  Comprehensive SMART error log
0x03       GPL     R/O  16383  Ext. Comprehensive SMART error log
0x04       GPL,SL  R/O    255  Device Statistics log
0x06           SL  R/O      1  SMART self-test log
0x07       GPL     R/O   3449  Extended self-test log
0x09           SL  R/W      1  Selective self-test log
0x10       GPL     R/O      1  NCQ Command Error log
0x11       GPL     R/O      1  SATA Phy Event Counters log
0x80-0x9f  GPL,SL  R/W     16  Host vendor specific log
0xa0       GPL     VS    2000  Device vendor specific log
0xa0       SL      VS     208  Device vendor specific log
0xa1-0xbf  GPL,SL  VS       1  Device vendor specific log
0xc0       GPL     VS      80  Device vendor specific log
0xc1-0xdf  GPL,SL  VS       1  Device vendor specific log
0xe0       GPL,SL  R/W      1  SCT Command/Status
0xe1       GPL,SL  R/W      1  SCT Data Transfer

SMART Extended Comprehensive Error Log Version: 1 (16383 sectors)
No Errors Logged

SMART Extended Self-test Log size 3449 not supported

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       50%     19433         244627776
# 2  Short offline       Completed: read failure       60%     19433         492159152
# 3  Short offline       Completed: read failure       60%     16715         492159152
# 4  Vendor (0xff)       Completed without error       00%     16602         -
# 5  Vendor (0xff)       Completed without error       00%      5107         -

SMART Selective self-test log data structure revision number 1
    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.

SCT Status Version:                  3
SCT Version (vendor specific):       1 (0x0001)
Device State:                        Active (0)
Current Temperature:                     0 Celsius
Power Cycle Min/Max Temperature:     --/ 0 Celsius
Lifetime    Min/Max Temperature:     --/ 0 Celsius

SCT Temperature History Version:     2
Temperature Sampling Period:         10 minutes
Temperature Logging Interval:        10 minutes
Min/Max recommended Temperature:      0/70 Celsius
Min/Max Temperature Limit:           -5/75 Celsius
Temperature History Size (Index):    478 (151)

Index    Estimated Time   Temperature Celsius
 152    2023-04-02 04:00     ?  -
 ...    ..(473 skipped).    ..  -
 148    2023-04-05 11:00     ?  -
 149    2023-04-05 11:10     0  -
 150    2023-04-05 11:20     0  -
 151    2023-04-05 11:30     0  -

SMART WRITE LOG does not return COUNT and LBA_LOW register
SCT (Get) Error Recovery Control command failed

Device Statistics (GP Log 0x04)
Page  Offset Size        Value Flags Description
0x01  =====  =               =  ===  == General Statistics (rev 2) ==
0x01  0x008  4             626  ---  Lifetime Power-On Resets
0x01  0x010  4           19434  ---  Power-on Hours
0x01  0x018  6     66167492621  ---  Logical Sectors Written
0x01  0x020  6      1499672681  ---  Number of Write Commands
0x01  0x028  6    138123876618  ---  Logical Sectors Read
0x01  0x030  6      2013843720  ---  Number of Read Commands
0x04  =====  =               =  ===  == General Errors Statistics (rev 1) ==
0x04  0x008  4             582  ---  Number of Reported Uncorrectable Errors
0x04  0x010  4               0  ---  Resets Between Cmd Acceptance and Completion
0x05  =====  =               =  ===  == Temperature Statistics (rev 1) ==
0x05  0x008  1               0  ---  Current Temperature
0x05  0x010  1               0  ---  Average Short Term Temperature
0x05  0x018  1               0  ---  Average Long Term Temperature
0x05  0x020  1               0  ---  Highest Temperature
0x05  0x028  1               0  ---  Lowest Temperature
0x05  0x030  1               0  ---  Highest Average Short Term Temperature
0x05  0x038  1               0  ---  Lowest Average Short Term Temperature
0x05  0x040  1               0  ---  Highest Average Long Term Temperature
0x05  0x048  1               0  ---  Lowest Average Long Term Temperature
0x05  0x050  4               -  ---  Time in Over-Temperature
0x05  0x058  1              70  ---  Specified Maximum Operating Temperature
0x05  0x060  4               -  ---  Time in Under-Temperature
0x05  0x068  1               0  ---  Specified Minimum Operating Temperature
0x06  =====  =               =  ===  == Transport Statistics (rev 1) ==
0x06  0x008  4           13903  ---  Number of Hardware Resets
0x06  0x010  4               0  ---  Number of ASR Events
0x06  0x018  4               3  ---  Number of Interface CRC Errors
0x07  =====  =               =  ===  == Solid State Device Statistics (rev 1) ==
0x07  0x008  1               4  N--  Percentage Used Endurance Indicator
                                |||_ C monitored condition met
                                ||__ D supports DSN
                                |___ N normalized value

SATA Phy Event Counters (GP Log 0x11)
ID      Size     Value  Description
0x0001  4            0  Command failed due to ICRC error
0x000a  4            0  Device-to-host register FISes sent due to a COMRESET

Crucial's own SMART report:

enter image description here enter image description here

I'm not too sure how to interpret the gsmartctl output, but I'm not convinced that the SMART PASSED result is correct. Time to bin and replace this drive?

  • 1
    Crucial m4, wow. That’s a ten year old SSD. IIRC it also had firmware bugs.
    – Daniel B
    Apr 5 at 12:12
  • Aye, 2013, according to the website. iirc the first version had fw bugs. I checked this one with Crucial's tools this morning as they said its on the latest fw. (Also said there's no problem with it....)
    – Ian
    Apr 5 at 12:21
  • Yes, firmware version 0309 appears to be the fixed version without the hang bug. // I would guess that smartctl misinterprets much of the data, because SMART was even less documented back then than it is today.
    – Daniel B
    Apr 5 at 12:28
  • 3
    Judging from Crucial's report of ID 242, I'm not sure Crucial does a much better job.
    – Ian
    Apr 5 at 12:39
  • 1
    Data corruption is a clear sign that a storage device is not to be trusted anymore. It has to be erased and disposed of properly.
    – fraxinus
    Apr 6 at 16:20

3 Answers 3


Forget looking at traffic light type self-tests. You have been given a wealth of information (SMART figures) that you just need to evaluate. Manufacturers don't have an interest to show a negative check result anyway. Maybe one should replace all Airbus instruments in the cockpit by two giant lights, coloured red and green, representing "passed" and "failed"? :)

As opposed to what others say, ignore the normalized value because there is no defined norm for the normalization process. Therefore the same RAW input gives different output in normalized terms between one manufacturer and another.

On a HDD anything above 0 as a raw value for the reallocated sector count is a failure indicator - some other user wrote this here on Superuser referring to either Google or Backblaze. As opposed to a HDD, sector or rather flash block reallocation is part of the use process of an SSD. In your case 36864 is a huge number in the HDD world, for a SSD it might not matter. I would rather look at the wear indicator ID 202. Do not expect linear growth as this indicator might take into account the number of spare flash blocks and another calculus.

Destructive partitioning of your SSD

Due to the lack of my experience with SMART figures from SSDs (as opposed to HDDs) I can't answer your question but in case you want to keep this SSD, please have a look at the ID 181. This SMART argument suggests that you have partitioned your SSD the wrong way causing write amplification, adding wear to your SSD.


Most likely you used a legacy operating system like for instance Windows XP in 32 bit when you partitioned the SSD. XP 32 bit tries to place partition starts on cylinder boundaries instead of multiples of a Megabyte (2^20). That way of operation is conflicting with the need to place partition starts on non-fractional multiples of the internal physical sector size. In your case the starting LBA number of your partition(s) should be dividable by 4096. (Necessary condition: LBA number MOD 4096=0). That is not the case now.

Copy the content of your SSD to a safe location, delete your partition table and repartition the SSD with a modern operating system. That modern OS will most likely put partition starts on multiples of 1 Megabyte which will comply with the above condition as well. Copy your content then back to your SSD. By doing so you are relieving future wear from your SSD as you reduce the write amplification.

You can use Testdisk to write a log file containing your current partition scheme. I guess there are suitable parameters for lsblkor fdisk as well.

  • A tale of caution on raw values: Many Seagate HDDs have misleading raw values that pack both the error count and the operation count into the same value. I almost returned a brand new drive because I heard a clicking sound and the seek errors were rising by several per second. It turns out the raw value of Seek_Error_Rate was just the total number of seeks (not errors), and this model of drive seeks loudly. There was no problem with the drive.
    – user253751
    Apr 6 at 20:26
  • You may have something here. Also see superuser.com/a/718581/705502 Apr 7 at 0:16
  • @user253751 Seagate SMART is documented, see disktuna.com/… Apr 7 at 0:29

I'm not sure that gsmartcontrol really understands and reports correctly all the SMART attributes, or that the disk firmware is correctly reporting its SMART attributes.

The SMART attributes show some errors and a weak disk, but not a catastrophic state, and yet the self-test fails and you report some file corruption.

Most puzzling is the "Reallocated Sector Count" whose raw count is 36864, which is catastrophic, but its normalized value is quite good at 99, which is only slightly below the best value of 100.

Unless you like living dangerously, I would in your place replace this disk.

I see you have added Crucial's own SMART report, which is much clearer than that of gsmartcontrol.

These are the danger signs :

364544 Retired NAND Blocks
20     NAND Page Program Failures
64     NAND Block Erase Failures
582    ECC Correction Failures
353    Corrected ECC

The worst data here is the number of Retired NAND Blocks, as defined by Cruclial's SSDs and SMART Data:

Attribute 5: Retired NAND Blocks

The number of blocks retired through this process of continually evaluating the quality of NAND blocks is tracked in SMART Attribute 5. SSD firmware will retire NAND blocks for several reasons in addition to the wear and data retention issue described above. One reason for retirement is a failure to erase a block while deleting data or moving data during garbage collection. This type of failure causes a low risk to user data since the data in question is being deleted or has already been copied successfully to a new location on the SSD.

This means that 364544 blocks on the disk have been become unusable with old age! This is enormous.

Final prognosis : The disk is failing and approaching its end of life. You should replace it as soon as possible.

  • 1
    Fwiw, Crucial's own tool describes ID 5 as "5 Retired NAND Blocks 364544 NAND Blocks"
    – Ian
    Apr 5 at 12:25
  • That would be even worse, if we for example assume 1 MiB sized blocks and couldn't even be right on this device. This is one of the situations where even the manufacturer's tool is wrong. Apr 5 at 13:03
  • 5
    Might not apply to this disk, but I have some Seagate HDDs which play tricks with the raw SMART values. On these drives, the "seek error count" packs the total number of seeks into the lower bits which makes it look like it is failing very frequently.
    – user253751
    Apr 5 at 18:45
  • 1
    Again a posting where harrymc is categorizing a storage device as "weak" without explaining what his "weak" is supposed to mean.
    – r2d3
    Apr 5 at 20:12
  • 1
    @JoepvanSteen: If those are 4K blocks (which might be the write-block size, smaller than the erase-block size) that's 1424 MiB of retired blocks (which is still pretty large). That seems plausible to me, especially if re-erasing a NAND block that was never written doesn't add extra wear. (Which I think it wouldn't, since you don't have charge carriers migrating back and forth.) So it would make sense that wear (and wearing out) would happen on a per-write-block basis, not whole erase blocks. Apr 5 at 21:01

In the SMART output, "pass" or "fail" is simply a one-line summary of the "SMART attributes" table. If none of the numbers in the "Value" or "Worst" columns is below the corresponding value in the "Threshold" column, it reports a "pass".

If a self-test is failing for any reason other than the test being canceled, the drive should be replaced, even if the SMART summary still says things are fine. With hard drives, SMART could only predict about half of all failures (and the SMART summary predicted even fewer). I don't think anybody's done a large-scale study of SMART on SSDs.

  • 1
    I once had a hard drive that was consistently reporting CRC errors and causing my computer to crash - due to a loose data cable. I would say if there's any known cause for the test to fail then you can ignore the fact that it failed. For example the data cable was loose or the power went out.
    – user253751
    Apr 6 at 20:28
  • 2
    @user253751, with the drives I'm familiar with, neither of the things you describe would cause a test to fail: a test will automatically resume if it's interrupted by a power failure, and once a drive is told to start running a test, it will do so autonomously until it either finishes, encounters an error, or is told to stop.
    – Mark
    Apr 6 at 23:07

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