Cause of Current Pending Sector and Offline Uncorrectable increase and then decrease to zero
Over the course of a week, for a 3TB Seagate drive (ST3000DM001-1CH166), smartd reported a slowly increasing number of offline uncorrectable and currently unreadable (pending) sectors, then a decreasing number, until finally the count was 0 and the error condition reset. From the logs (showing only changes):
Jul 6 18:04:57 x smartd[462]: Device: /dev/sdb [SAT], 8 Currently unreadable (pending) sectors
Jul 6 18:04:58 x smartd[462]: Device: /dev/sdb [SAT], 8 Offline uncorrectable sectors
[...]
Jul 7 16:34:58 x smartd[462]: Device: /dev/sdb [SAT], 16 Currently unreadable (pending) sectors (changed +8)
Jul 7 16:34:58 x smartd[462]: Device: /dev/sdb [SAT], 16 Offline uncorrectable sectors (changed +8)
[...]
Jul 11 14:04:57 x smartd[462]: Device: /dev/sdb [SAT], 24 Currently unreadable (pending) sectors (changed +8)
Jul 11 14:04:57 x smartd[462]: Device: /dev/sdb [SAT], 24 Offline uncorrectable sectors (changed +8)
Jul 11 14:34:57 x smartd[462]: Device: /dev/sdb [SAT], 32 Currently unreadable (pending) sectors (changed +8)
Jul 11 14:34:58 x smartd[462]: Device: /dev/sdb [SAT], 32 Offline uncorrectable sectors (changed +8)
[...]
Jul 13 09:04:57 x smartd[462]: Device: /dev/sdb [SAT], 24 Currently unreadable (pending) sectors (changed -8)
Jul 13 09:04:57 x smartd[462]: Device: /dev/sdb [SAT], 24 Offline uncorrectable sectors (changed -8)
Jul 13 09:34:58 x smartd[462]: Device: /dev/sdb [SAT], 16 Currently unreadable (pending) sectors (changed -8)
Jul 13 09:34:58 x smartd[462]: Device: /dev/sdb [SAT], 16 Offline uncorrectable sectors (changed -8)
Jul 13 10:04:57 x smartd[462]: Device: /dev/sdb [SAT], 16 Currently unreadable (pending) sectors
Jul 13 10:04:57 x smartd[462]: Device: /dev/sdb [SAT], 16 Offline uncorrectable sectors
Jul 13 10:34:57 x smartd[462]: Device: /dev/sdb [SAT], No more Currently unreadable (pending) sectors, warning condition reset after 1 email
Jul 13 10:34:57 x smartd[462]: Device: /dev/sdb [SAT], No more Offline uncorrectable sectors, warning condition reset after 1 email
Furthermore, the reallocated sector count is also 0, so the sectors do not appear to have been re-mapped. Here is the complete (current) smartctl -a output for the drive:
smartctl 6.2 2013-07-26 r3841 [x86_64-linux-3.14.4-100.fc19.x86_64] (local build)
Copyright (C) 2002-13, Bruce Allen, Christian Franke, www.smartmontools.org
=== START OF INFORMATION SECTION ===
Model Family: Seagate Barracuda 7200.14 (AF)
Device Model: ST3000DM001-1CH166
Serial Number: W1F30FK2
LU WWN Device Id: 5 000c50 06129a9a8
Firmware Version: CC27
User Capacity: 3,000,592,982,016 bytes [3.00 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: 7200 rpm
Device is: In smartctl database [for details use: -P show]
ATA Version is: ACS-2, ACS-3 T13/2161-D revision 3b
SATA Version is: SATA 3.1, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is: Wed Jul 16 11:23:08 2014 EDT
==> WARNING: A firmware update for this drive may be available,
see the following Seagate web pages:
http://knowledge.seagate.com/articles/en_US/FAQ/207931en
http://knowledge.seagate.com/articles/en_US/FAQ/223651en
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: ( 584) 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: ( 347) minutes.
Conveyance self-test routine
recommended polling time: ( 2) minutes.
SCT capabilities: (0x3085) SCT Status 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 115 099 006 Pre-fail Always - 91131424
3 Spin_Up_Time 0x0003 094 094 000 Pre-fail Always - 0
4 Start_Stop_Count 0x0032 100 100 020 Old_age Always - 12
5 Reallocated_Sector_Ct 0x0033 100 100 010 Pre-fail Always - 0
7 Seek_Error_Rate 0x000f 078 060 030 Pre-fail Always - 59138260
9 Power_On_Hours 0x0032 094 094 000 Old_age Always - 5888
10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always - 0
12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always - 12
183 Runtime_Bad_Block 0x0032 100 100 000 Old_age Always - 0
184 End-to-End_Error 0x0032 100 100 099 Old_age Always - 0
187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always - 0
188 Command_Timeout 0x0032 100 100 000 Old_age Always - 0 0 0
189 High_Fly_Writes 0x003a 097 097 000 Old_age Always - 3
190 Airflow_Temperature_Cel 0x0022 053 049 045 Old_age Always - 47 (Min/Max 23/51)
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 - 10
193 Load_Cycle_Count 0x0032 096 096 000 Old_age Always - 8086
194 Temperature_Celsius 0x0022 047 051 000 Old_age Always - 47 (0 22 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
240 Head_Flying_Hours 0x0000 100 253 000 Old_age Offline - 5703h+56m+25.808s
241 Total_LBAs_Written 0x0000 100 253 000 Old_age Offline - 11838196191
242 Total_LBAs_Read 0x0000 100 253 000 Old_age Offline - 211237637103
SMART Error Log Version: 1
No Errors Logged
SMART Self-test log structure revision number 1
No self-tests have been logged. [To run self-tests, use: smartctl -t]
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.
I have downloaded but not yet run Seatools on the drive, but the current SMART status of the drive basically seems fine. What could cause such behavior?
UPDATE: For future readers, the drive was actually fine for a couple more months, at which point more sectors become uncorrectable/offline, and the number of reallocated sectors started increasing beyond 0, and the SMART long self-test started failing with a read error. So these messages appeared to be a useful early warning.
Solution 1:
I've had this a few times recently with a similar Seagate ST3000DM001-1CH166 firmware CC24. You don't need Seatools, just run a long smart test:
smartctl -t long /dev/sdc
Then if smarctl shows no error you're OK for now:
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% 9912 -
If it fails then send straight back to Seagate. They replaced my last failed one in about a week.
Solution 2:
Current Pending Sector is just that, the number of locations the disk knows about that needs to be reallocated but haven't reallocated yet since the disk has no source for the data to be reallocated. Once you write into that location the disk will automatically reallocate the area to another place and write the new data in the new place and the current pending sector cound will decrease.
This is all perfectly fine and how the disk should operate.
You can use diskscan on Linux or HD Tune on Windows to scan the disk for the bad locations and also attempt to "fix" the locations by making the software write into them in order to attempt the reallocation immediately.