I woke up this morning on that the smartd was reporting an error: “smartd[1209]: Device: /dev/ad3, 1 Currently unreadable (pending) sectors” from one of the physical devices that was connected to my mirrored device. When I googled I found explanation:
Current count of unstable sectors (waiting for remapping). The raw value of this attribute indicates the total number of sectors waiting for remapping. Later, when some of these sectors are read successfully, the value is decreased. If errors still occur when reading some sector, the hard drive will try to restore the data, transfer it to the reserved disk area (spare area) and mark this sector as remapped. If this attribute value remains at zero, it indicates that the quality of the corresponding surface area is low.
smartctl -a /dev/ad3 showed the following:
... 196 Reallocated_Event_Count 0x0032 200 200 000 Old_age Always - 0 197 Current_Pending_Sector 0x0032 200 200 000 Old_age Always - 1 198 Offline_Uncorrectable 0x0030 200 200 000 Old_age Offline - 0 ...
So what needed to be done was to force the drive to write the area with new data and thus getting the sector either remapped or cleared from the error. As the disk was a mirrored drive and the other drive was working properly (+ I have backups in case of horror) I decided that I can remove the drive from the mirror using gmirror remove. Then I ran a long test with smartctl -t long /dev/ad3 and it reported no errors. After that I inserted the drive back to the mirror and as the drive was resynchronized S.M.A.R.T. Current_Pending_Sector value was decreased:
... 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 200 200 000 Old_age Offline - 0 ...
The drive didn’t increase the Reallocated_Sector_Ct.
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Update: Although I managed to correct the pending sectors couple of days after the first error occurred the drive started to fail totally. So tweaking and fixing was not very helpful as the errors started to escalate. In conclusion I decided to change the drive.
Smartd status just before I removed the drive:
smartd[1209]: Device: /dev/ad3, 348 Currently unreadable (pending) sectors
smartd[1209]: Device: /dev/ad3, 257 Offline uncorrectable sectors
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 - 1 3 Spin_Up_Time 0x0027 239 238 021 Pre-fail Always - 1050 4 Start_Stop_Count 0x0032 100 100 000 Old_age Always - 54 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 084 084 000 Old_age Always - 12022 10 Spin_Retry_Count 0x0032 100 253 000 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 - 52 192 Power-Off_Retract_Count 0x0032 200 200 000 Old_age Always - 51 193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 2 194 Temperature_Celsius 0x0022 124 107 000 Old_age Always - 23 196 Reallocated_Event_Count 0x0032 200 200 000 Old_age Always - 0 197 Current_Pending_Sector 0x0032 196 196 000 Old_age Always - 348 198 Offline_Uncorrectable 0x0030 197 197 000 Old_age Offline - 257 199 UDMA_CRC_Error_Count 0x0032 200 200 000 Old_age Always - 0 200 Multi_Zone_Error_Rate 0x0008 001 001 000 Old_age Offline - 24383