Error: Currently unreadable (pending) sectors

Asrik · January 12, 2026, 8:35pm

Hello everyone. I received my first error from truenas scale. I been looking around on the net and I was not able to find any usefully information about this error, only that the disk might be dying. I reboot the truenas VM in hope that it might just self resolve something.. While that was rebooting I found a command I could need to check status of the disk and status from smartctl. It looks like im not getting any errors anymore but I want to make sure im looking at this correctly.

I have added a screenshot of the log and results of the two commands i used.

root@home-nas[~]# sudo zpool status -v
  pool: LargeNASPool
 state: ONLINE
config:

        NAME                                      STATE     READ WRITE CKSUM
        LargeNASPool                              ONLINE       0     0     0
          raidz1-0                                ONLINE       0     0     0
            3074bf13-301c-4ea8-ac1b-7d6a9d442cae  ONLINE       0     0     0
            f4e462cb-ab9e-49a1-9219-42dbffff6c12  ONLINE       0     0     0
            26942678-970a-41ec-9d9f-68e26553cdc5  ONLINE       0     0     0
        logs
          5bbc06e0-f085-482d-b4ed-7b427e7e5cc4    ONLINE       0     0     0

errors: No known data errors

  pool: NASMainStorage
 state: ONLINE
  scan: scrub repaired 0B in 02:09:21 with 0 errors on Sun Jan  4 02:09:27 2026
config:

        NAME            STATE     READ WRITE CKSUM
        NASMainStorage  ONLINE       0     0     0
          raidz1-0      ONLINE       0     0     0
            sdb2        ONLINE       0     0     0
            sdc2        ONLINE       0     0     0
            sde2        ONLINE       0     0     0
            sdd2        ONLINE       0     0     0
        logs
          sdj1          ONLINE       0     0     0

errors: No known data errors

  pool: boot-pool
 state: ONLINE
  scan: scrub repaired 0B in 00:00:36 with 0 errors on Mon Jan 12 03:45:37 2026
config:

        NAME        STATE     READ WRITE CKSUM
        boot-pool   ONLINE       0     0     0
          sda3      ONLINE       0     0     0

errors: No known data errors

root@home-nas[~]# sudo smartctl -a /dev/sdj
smartctl 7.4 2023-08-01 r5530 [x86_64-linux-6.6.44-production+truenas] (local build)
Copyright (C) 2002-23, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Samsung based SSDs
Device Model:     Samsung SSD 850 EVO 250GB
Serial Number:    S2R5NB0HA56373R
LU WWN Device Id: 5 002538 d41552100
Firmware Version: EMT02B6Q
User Capacity:    250,059,350,016 bytes [250 GB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    Solid State Device
Form Factor:      2.5 inches
TRIM Command:     Available
Device is:        In smartctl database 7.3/6061
ATA Version is:   ACS-2, ATA8-ACS T13/1699-D revision 4c
SATA Version is:  SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Mon Jan 12 15:13:16 2026 EST
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:                (    0) seconds.
Offline data collection
capabilities:                    (0x53) SMART execute Offline immediate.
                                        Auto Offline data collection on/off support.
                                        Suspend Offline collection upon new
                                        command.
                                        No 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:        ( 133) 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: 1
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  5 Reallocated_Sector_Ct   0x0033   100   100   010    Pre-fail  Always       -       0
  9 Power_On_Hours          0x0032   093   093   000    Old_age   Always       -       34841
 12 Power_Cycle_Count       0x0032   097   097   000    Old_age   Always       -       2132
177 Wear_Leveling_Count     0x0013   098   098   000    Pre-fail  Always       -       40
179 Used_Rsvd_Blk_Cnt_Tot   0x0013   100   100   010    Pre-fail  Always       -       0
181 Program_Fail_Cnt_Total  0x0032   100   100   010    Old_age   Always       -       0
182 Erase_Fail_Count_Total  0x0032   100   100   010    Old_age   Always       -       0
183 Runtime_Bad_Block       0x0013   100   100   010    Pre-fail  Always       -       0
187 Uncorrectable_Error_Cnt 0x0032   100   100   000    Old_age   Always       -       0
190 Airflow_Temperature_Cel 0x0032   070   039   000    Old_age   Always       -       30
195 ECC_Error_Rate          0x001a   200   200   000    Old_age   Always       -       0
199 CRC_Error_Count         0x003e   096   096   000    Old_age   Always       -       3174
235 POR_Recovery_Count      0x0012   099   099   000    Old_age   Always       -       552
241 Total_LBAs_Written      0x0032   099   099   000    Old_age   Always       -       20319037698

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 without error       00%     34802         -
# 2  Short offline       Completed without error       00%     34634         -
# 3  Short offline       Completed without error       00%     34466         -
# 4  Short offline       Completed without error       00%     34298         -
# 5  Short offline       Completed without error       00%     34249         -
# 6  Short offline       Completed without error       00%     34081         -
# 7  Short offline       Completed without error       00%     33913         -
# 8  Short offline       Completed without error       00%     33746         -
# 9  Short offline       Completed without error       00%     33578         -
#10  Short offline       Completed without error       00%     33410         -
#11  Short offline       Completed without error       00%     33241         -
#12  Short offline       Completed without error       00%     33073         -
#13  Short offline       Completed without error       00%     32905         -
#14  Short offline       Completed without error       00%     32737         -
#15  Short offline       Completed without error       00%     32569         -
#16  Short offline       Completed without error       00%     32401         -
#17  Short offline       Completed without error       00%     32233         -
#18  Short offline       Completed without error       00%     32078         -
#19  Short offline       Completed without error       00%     31910         -
#20  Short offline       Completed without error       00%     31742         -
#21  Short offline       Completed without error       00%     31574         -

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
  255        0    65535  Read_scanning was never started
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.

The above only provides legacy SMART information - try 'smartctl -x' for more

Thank you for your help and time.

xMAXIMUSx · January 12, 2026, 9:03pm

It could have been fluke and after the system scrubbed the data it corrected itself.

Or the drive is starting to show signs of failure and you might want to look into swapping it. If it was me and this is a boot pool that is redundant then I’d dismiss the alert and keep an eye on it. If more errors come in later then I’d replace it.

Moseph_V · January 12, 2026, 9:14pm

I agree 100%. If tests are looking good now, it could have been a transient issue.

One thing to maybe consider is the rising prices of flash storage, or even storage in general. I know it’s mostly NVMe at this point, but even spinning rust seems to be getting caught up in it. Plus there are rumours (take with a healthy grain of salt) that Samsung is planning on stopping SATA SSD production this year. Regardless, the point is that if you’re worried about having to replace it, now may be a good time to get a spare drive on hand.

Plus, while SSD’s are generally more reliable than their HDD counterparts, they’re also known to die really fast on occasion, when their time comes.

Asrik · January 12, 2026, 9:19pm

Thanks for the reply. I was about to say. If the SSD is about to fail, i would buy a replacement now before the prices go up again. I forgot to mention that this SSD is setup as a LOG drive, so im not worried if it fails..

PS I hope the Samsung rumours are not true….

Asrik · January 13, 2026, 2:49pm

Ok.. so now I have another error but on a different disk.

I ran the two commands again.

root@home-nas[~]# sudo zpool status -v
  pool: LargeNASPool
 state: ONLINE
config:

        NAME                                      STATE     READ WRITE CKSUM
        LargeNASPool                              ONLINE       0     0     0
          raidz1-0                                ONLINE       0     0     0
            3074bf13-301c-4ea8-ac1b-7d6a9d442cae  ONLINE       0     0     0
            f4e462cb-ab9e-49a1-9219-42dbffff6c12  ONLINE       0     0     0
            26942678-970a-41ec-9d9f-68e26553cdc5  ONLINE       0     0     0
        logs
          5bbc06e0-f085-482d-b4ed-7b427e7e5cc4    ONLINE       0     0     0

errors: No known data errors

  pool: NASMainStorage
 state: DEGRADED
status: One or more devices are faulted in response to persistent errors.
        Sufficient replicas exist for the pool to continue functioning in a
        degraded state.
action: Replace the faulted device, or use 'zpool clear' to mark the device
        repaired.
  scan: scrub repaired 0B in 02:09:21 with 0 errors on Sun Jan  4 02:09:27 2026
config:

        NAME            STATE     READ WRITE CKSUM
        NASMainStorage  DEGRADED     0     0     0
          raidz1-0      DEGRADED     0     0     0
            sdb2        ONLINE       0     0     0
            sdc2        ONLINE       0     0     0
            sde2        ONLINE       0     0     0
            sdd2        FAULTED     71     0     0  too many errors
        logs
          sdj1          ONLINE       0     0     0

errors: No known data errors

  pool: boot-pool
 state: ONLINE
  scan: scrub repaired 0B in 00:00:36 with 0 errors on Mon Jan 12 03:45:37 2026
config:

        NAME        STATE     READ WRITE CKSUM
        boot-pool   ONLINE       0     0     0
          sda3      ONLINE       0     0     0

errors: No known data errors

root@home-nas[~]# sudo smartctl -a /dev/sdd
smartctl 7.4 2023-08-01 r5530 [x86_64-linux-6.6.44-production+truenas] (local build)
Copyright (C) 2002-23, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Seagate IronWolf
Device Model:     ST2000VN004-2E4164
Serial Number:    Z52BWDLY
LU WWN Device Id: 5 000c50 0e4590085
Firmware Version: SC60
User Capacity:    2,000,398,934,016 bytes [2.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    5900 rpm
Form Factor:      3.5 inches
Device is:        In smartctl database 7.3/6061
ATA Version is:   ACS-2, ACS-3 T13/2161-D revision 3b
SATA Version is:  SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Tue Jan 13 09:36:20 2026 EST
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:                (   97) seconds.
Offline data collection
capabilities:                    (0x73) SMART execute Offline immediate.
                                        Auto Offline data collection on/off support.
                                        Suspend Offline collection upon new
                                        command.
                                        No 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:        (   1) minutes.
Extended self-test routine
recommended polling time:        ( 250) minutes.
Conveyance self-test routine
recommended polling time:        (   2) minutes.
SCT capabilities:              (0x10bd) SCT Status supported.
                                        SCT Error Recovery Control supported.
                                        SCT Feature Control supported.
                                        SCT Data Table supported.

SMART Attributes Data Structure revision number: 10
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   111   099   006    Pre-fail  Always       -       0/128125852
  3 Spin_Up_Time            0x0003   097   096   000    Pre-fail  Always       -       0
  4 Start_Stop_Count        0x0032   100   100   020    Old_age   Always       -       58
  5 Reallocated_Sector_Ct   0x0033   100   100   010    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x000f   079   060   030    Pre-fail  Always       -       0/90485666
  9 Power_On_Hours          0x0032   071   071   000    Old_age   Always       -       25558
 10 Spin_Retry_Count        0x0013   100   100   097    Pre-fail  Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   020    Old_age   Always       -       37
184 End-to-End_Error        0x0032   100   100   099    Old_age   Always       -       0
187 Reported_Uncorrect      0x0032   096   096   000    Old_age   Always       -       4
188 Command_Timeout         0x0032   100   100   000    Old_age   Always       -       0 0 0
189 High_Fly_Writes         0x003a   067   067   000    Old_age   Always       -       33
190 Airflow_Temperature_Cel 0x0022   071   060   045    Old_age   Always       -       29 (Min/Max 24/35)
191 G-Sense_Error_Rate      0x0032   100   100   000    Old_age   Always       -       0
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       31
193 Load_Cycle_Count        0x0032   090   090   000    Old_age   Always       -       21055
194 Temperature_Celsius     0x0022   029   040   000    Old_age   Always       -       29 (0 17 0 0 0)
197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0010   100   100   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -       0

SMART Error Log Version: 1
ATA Error Count: 4
        CR = Command Register [HEX]
        FR = Features Register [HEX]
        SC = Sector Count Register [HEX]
        SN = Sector Number Register [HEX]
        CL = Cylinder Low Register [HEX]
        CH = Cylinder High Register [HEX]
        DH = Device/Head Register [HEX]
        DC = Device Command Register [HEX]
        ER = Error register [HEX]
        ST = Status register [HEX]
Powered_Up_Time is measured from power on, and printed as
DDd+hh:mm:SS.sss where DD=days, hh=hours, mm=minutes,
SS=sec, and sss=millisec. It "wraps" after 49.710 days.

Error 4 occurred at disk power-on lifetime: 25548 hours (1064 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 53 00 ff ff ff 0f  Error: WP at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  61 00 30 ff ff ff 4f 00  24d+12:01:31.091  WRITE FPDMA QUEUED
  60 00 78 ff ff ff 4f 00  24d+12:01:31.090  READ FPDMA QUEUED
  60 00 50 a0 69 71 4a 00  24d+12:01:31.089  READ FPDMA QUEUED
  61 00 08 ff ff ff 4f 00  24d+12:01:31.084  WRITE FPDMA QUEUED
  60 00 18 ff ff ff 4f 00  24d+12:01:31.084  READ FPDMA QUEUED

Error 3 occurred at disk power-on lifetime: 25548 hours (1064 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 53 00 ff ff ff 0f  Error: UNC at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 00 b8 ff ff ff 4f 00  24d+12:01:26.485  READ FPDMA QUEUED
  60 00 a0 ff ff ff 4f 00  24d+12:01:26.484  READ FPDMA QUEUED
  60 00 50 48 30 52 4a 00  24d+12:01:26.484  READ FPDMA QUEUED
  60 00 38 ff ff ff 4f 00  24d+12:01:26.480  READ FPDMA QUEUED
  60 00 a8 ff ff ff 4f 00  24d+12:01:26.479  READ FPDMA QUEUED

Error 2 occurred at disk power-on lifetime: 25548 hours (1064 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 53 00 ff ff ff 0f  Error: WP at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  61 00 e0 ff ff ff 4f 00  24d+12:01:22.095  WRITE FPDMA QUEUED
  61 00 a0 ff ff ff 4f 00  24d+12:01:22.094  WRITE FPDMA QUEUED
  61 00 98 ff ff ff 4f 00  24d+12:01:22.094  WRITE FPDMA QUEUED
  61 00 08 ff ff ff 4f 00  24d+12:01:22.094  WRITE FPDMA QUEUED
  60 00 40 ff ff ff 4f 00  24d+12:01:22.092  READ FPDMA QUEUED

Error 1 occurred at disk power-on lifetime: 25548 hours (1064 days + 12 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 53 00 ff ff ff 0f  Error: UNC at LBA = 0x0fffffff = 268435455

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  60 00 c8 ff ff ff 4f 00  24d+12:01:17.964  READ FPDMA QUEUED
  60 00 88 ff ff ff 4f 00  24d+12:01:17.964  READ FPDMA QUEUED
  60 00 e0 ff ff ff 4f 00  24d+12:01:17.964  READ FPDMA QUEUED
  60 00 20 60 8d 85 4a 00  24d+12:01:17.939  READ FPDMA QUEUED
  60 00 08 ff ff ff 4f 00  24d+12:01:17.928  READ FPDMA QUEUED

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Short offline       Completed without error       00%     25538         -
# 2  Short offline       Completed without error       00%     25501         -
# 3  Short offline       Completed without error       00%     25333         -
# 4  Short offline       Completed without error       00%     25165         -
# 5  Short offline       Completed without error       00%     24997         -
# 6  Short offline       Completed without error       00%     24831         -
# 7  Short offline       Completed without error       00%     24663         -
# 8  Short offline       Completed without error       00%     24496         -
# 9  Short offline       Completed without error       00%     24327         -
#10  Short offline       Completed without error       00%     24159         -
#11  Short offline       Completed without error       00%     23991         -
#12  Short offline       Completed without error       00%     23822         -
#13  Short offline       Completed without error       00%     23655         -
#14  Short offline       Completed without error       00%     23486         -
#15  Short offline       Completed without error       00%     23318         -
#16  Short offline       Completed without error       00%     23151         -
#17  Short offline       Completed without error       00%     22983         -
#18  Short offline       Completed without error       00%     22816         -
#19  Short offline       Completed without error       00%     22660         -
#20  Short offline       Completed without error       00%     22492         -
#21  Short offline       Completed without error       00%     22324         -

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.

The above only provides legacy SMART information - try 'smartctl -x' for more

Since this error started at midnight, I also had a Replication Tasks from poolA to poolB which also started at midnight. Could the error happened because of this Replication Tasks?

I want to add that this pool has a few VM running on it which also has lots of disk I/O.

(looks like disk sdd is either dead or offline…………)

What would be the best why to mitigate the chance or issue could happen in the future? Would a “Periodic S.M.A.R.T. Tests” and/or “Scrub Tasks” help with this?

Asrik · January 13, 2026, 4:01pm

I just rebooted the TrueNAS VM. It resilvered the pool and now disk sde has errors…… ran “sudo smartctl -a /dev/sde” it shows the same serial number. That seems the disk is dying.. Maybe spinrite could fix it??

Asrik · January 13, 2026, 5:07pm

I have been looking for a replacement. My model is discontinued. Im thinking to get a 2TB but 7200rpm, thinking it would be better to have a higher rpm then a 4TB 5400rpm…. or it shouldn’t matter?

Thoughts?

pavlos · January 13, 2026, 9:10pm

if your pool has 2TB disks, you need to replace with a 2TB disk.

I have truenas with four 8TB disks, one failed, it continues running degraded with 3.
The price of a 8TB is too much for me.

Moseph_V · January 13, 2026, 10:20pm

You can replace a disk with a larger disk. Just note that the vdev will only use the space equal to that of the smallest disk (so a 4TB disk will only store 2TB max in this case it sounds like). Once all disks have been replaced with larger disks, than the total size will grow, once again, based on the size of the smallest disk.

Also note that TrueNAS will show a warning on the pool because of the mismatched disk size.

Asrik · January 13, 2026, 11:32pm

Thanks.. That is what i thought with getting a larger compacity.. But not sure if there will be a huge issue with the rpm.. Im sure Truenas will slow down any faster disk to match the others slower disk (im guessing here?) but I dont know if it still a good idea or if there wont be any issues…

Im thinking about more of reliability at this point…