Recently I got a critical alert in my TrueNAS dashboard about my Apps pool being degraded. When I go to storage, it shows as “Degraded, no errors.”
The pool consists of a single SSD as all important data is backed up to another drive. I cannot find any information on why the pool is actually degraded anywhere in the dashboard…. zpool status returns the following. It says “too many erorrs” and “No errors” at the same time…
pool: Apps
state: DEGRADED
status: One or more devices has experienced an unrecoverable error. An
attempt was made to correct the error. Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
using 'zpool clear' or replace the device with 'zpool replace'.
see: https://openzfs.github.io/openzfs-docs/msg/ZFS-8000-9P
scan: scrub repaired 0B in 00:04:14 with 0 errors on Wed Jul 15 18:49:46 2026
config:
NAME STATE READ WRITE CKSUM
Apps DEGRADED 0 0 0
9ef8a3ba-8af2-47ec-b84d-bfaf914018a1 DEGRADED 0 0 0 too many errors
errors: No known data errors
The SMART report also doesn’t seem to show anything problematic:
=== START OF INFORMATION SECTION ===
Model Family: Crucial/Micron Client SSDs
Device Model: CT250MX500SSD1
Serial Number: 1909E1EE85CF
LU WWN Device Id: 5 00a075 1e1ee85cf
Firmware Version: M3CR023
User Capacity: 250,059,350,016 bytes [250 GB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: Solid State Device
Form Factor: 2.5 inches
TRIM Command: Available
Device is: In smartctl database 7.3/5528
ATA Version is: ACS-3 T13/2161-D revision 5
SATA Version is: SATA 3.3, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is: Wed Jul 15 18:33:36 2026 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: ( 0) 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: ( 30) minutes.
Conveyance self-test routine
recommended polling time: ( 2) minutes.
SCT capabilities: (0x0031) 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 100 100 000 Pre-fail Always - 0
5 Reallocate_NAND_Blk_Cnt 0x0032 100 100 010 Old_age Always - 0
9 Power_On_Hours 0x0032 100 100 000 Old_age Always - 33374
12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 660
171 Program_Fail_Count 0x0032 100 100 000 Old_age Always - 0
172 Erase_Fail_Count 0x0032 100 100 000 Old_age Always - 0
173 Ave_Block-Erase_Count 0x0032 141 141 000 Old_age Always - 3226
174 Unexpect_Power_Loss_Ct 0x0032 100 100 000 Old_age Always - 74
180 Unused_Reserve_NAND_Blk 0x0033 000 000 000 Pre-fail Always - 31
183 SATA_Interfac_Downshift 0x0032 100 100 000 Old_age Always - 2
184 Error_Correction_Count 0x0032 100 100 000 Old_age Always - 0
187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always - 0
194 Temperature_Celsius 0x0022 065 039 000 Old_age Always - 35 (Min/Max 0/61)
196 Reallocated_Event_Count 0x0032 100 100 000 Old_age Always - 0
197 Current_Pending_ECC_Cnt 0x0032 100 100 000 Old_age Always - 0
198 Offline_Uncorrectable 0x0030 100 100 000 Old_age Offline - 0
199 UDMA_CRC_Error_Count 0x0032 100 100 000 Old_age Always - 36
202 Percent_Lifetime_Remain 0x0030 141 141 001 Old_age Offline - 215
206 Write_Error_Rate 0x000e 100 100 000 Old_age Always - 0
210 Success_RAIN_Recov_Cnt 0x0032 100 100 000 Old_age Always - 0
246 Total_LBAs_Written 0x0032 100 100 000 Old_age Always - 97108781451
247 Host_Program_Page_Count 0x0032 100 100 000 Old_age Always - 1925866677
248 FTL_Program_Page_Count 0x0032 100 100 000 Old_age Always - 27468873744
SMART Error Log Version: 1
Invalid Error Log index = 0x10 (valid range is from 1 to 5)
ATA Error Count: 0 (possibly also invalid)
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% 33361 -
# 2 Short offline Completed without error 00% 33341 -
# 3 Short offline Completed without error 00% 33321 -
# 4 Extended offline Completed without error 00% 33302 -
# 5 Short offline Completed without error 00% 33302 -
# 6 Short offline Completed without error 00% 23501 -
# 7 Extended offline Completed without error 00% 25021 -
# 8 Short offline Completed without error 00% 24957 -
# 9 Short offline Completed without error 00% 24871 -
#10 Short offline Completed without error 00% 24778 -
#11 Short offline Completed without error 00% 24686 -
#12 Extended offline Completed without error 00% 24634 -
#13 Short offline Completed without error 00% 24594 -
#14 Short offline Completed without error 00% 24502 -
#15 Short offline Completed without error 00% 24411 -
#16 Short offline Completed without error 00% 24318 -
#17 Extended offline Completed without error 00% 24232 -
#18 Short offline Completed without error 00% 24231 -
#19 Short offline Completed without error 00% 24139 -
#20 Short offline Completed without error 00% 24048 -
#21 Short offline Completed without error 00% 23955 -
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
Is there anything else I can check to find out what the problem is? Is it safe to just clear the error of the zpool and see if it repeats?