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SOLVED Pending sector

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HertogArjan

Dabbler
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Oct 16, 2016
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Hi everyone,

For a full week now my server has been warning me of an error concerning one of my drives. Apparently one of them has "1 currently unreadable (pending) sector". I had to look up what it actually meant, from what I understand now it is a sector which has not been reallocated yet and is in the process of doing so. I thought it would resolve itself, but as of yet it still has one current pending sector. The pending sector count has not increased, which is a good sign, and the other SMART statistics seem healthy enough in my opinion. It is an old drive and besides the pending sector nothing suggests the drive may be close to failing.

Code:
Model Family:	 Western Digital Red
Device Model:	 WDC WD30EFRX-68EUZN0
Firmware Version: 80.00A80
User Capacity:	3,000,592,982,016 bytes [3.00 TB]
Sector Sizes:	 512 bytes logical, 4096 bytes physical
Rotation Rate:	5400 rpm
Device is:		In smartctl database [for details use: -P show]
ATA Version is:   ACS-2 (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:	Sun Sep 24 14:17:43 2017 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:  (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:				(41040) 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:		( 412) minutes.
Conveyance self-test routine
recommended polling time:		(   5) minutes.
SCT capabilities:			  (0x703d) 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:
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	   -	   262
  3 Spin_Up_Time			0x0027   179   178   021	Pre-fail  Always	   -	   6050
  4 Start_Stop_Count		0x0032   100   100   000	Old_age   Always	   -	   314
  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   060   060   000	Old_age   Always	   -	   29692
10 Spin_Retry_Count		0x0032   100   100   000	Old_age   Always	   -	   0
11 Calibration_Retry_Count 0x0032   100   100   000	Old_age   Always	   -	   0
12 Power_Cycle_Count	   0x0032   100   100   000	Old_age   Always	   -	   187
192 Power-Off_Retract_Count 0x0032   200   200   000	Old_age   Always	   -	   143
193 Load_Cycle_Count		0x0032   200   200   000	Old_age   Always	   -	   435
194 Temperature_Celsius	 0x0022   122   110   000	Old_age   Always	   -	   28
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   100   253   000	Old_age   Offline	  -	   0
199 UDMA_CRC_Error_Count	0x0032   200   200   000	Old_age   Always	   -	   0
200 Multi_Zone_Error_Rate   0x0008   200   200   000	Old_age   Offline	  -	   0

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  Extended offline	Completed without error	   00%	 29667		 -
# 2  Short offline	   Completed without error	   00%	 29586		 -
# 3  Short offline	   Completed without error	   00%	 29529		 -
# 4  Extended offline	Completed without error	   00%	 29529		 -
# 5  Extended offline	Aborted by host			   10%	 29522		 -
# 6  Short offline	   Completed without error	   00%	 29394		 -
# 7  Extended offline	Completed without error	   00%	 29307		 -
# 8  Short offline	   Completed without error	   00%	 29202		 -
# 9  Short offline	   Completed without error	   00%	 29011		 -
#10  Extended offline	Completed without error	   00%	 28925		 -
#11  Short offline	   Completed without error	   00%	 28843		 -
#12  Short offline	   Completed without error	   00%	 28652		 -
#13  Short offline	   Completed without error	   00%	 28651		 -
#14  Short offline	   Completed without error	   00%	 28626		 -
#15  Short offline	   Completed without error	   00%	 28578		 -
#16  Extended offline	Completed without error	   00%	 28563		 -
#17  Short offline	   Completed without error	   00%	 28530		 -
#18  Short offline	   Completed without error	   00%	 28482		 -
#19  Short offline	   Completed without error	   00%	 28434		 -
#20  Short offline	   Completed without error	   00%	 28390		 -
#21  Short offline	   Completed without error	   00%	 28362		 -

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 want to somehow resolve the error. I looked at some other threads here on the forums, most interesting was this one: Is this a bad sign: smartd: 1 Currently unreadable (pending) sectors....?. It was suggested that the location of the corrupted sector could be determined with a long SMART test and then that sector could be overwritten with 0's. Sounded reasonable enough, although my SMART tests always completed without error. I was never able to find the location of the corrupted Sector. I tried long and short SMART tests, I offlined the drive for a while, I tried rebooting the system and I tried scrubbing the pool, but all finished without error and did not resolve the current pending sector. I thought it was especially interesting the scrub found no errors, since I would expect it to if one of the drives had a failing sector.

I hope someone is able to explain why the pending sector stays pending and whether it is possible to resolve this. I realise an obvious solution is to replace the drive, but since the error count is not increasing I think it is to soon to discard the drive.

Thanks in advance.
 

Ericloewe

Not-very-passive-but-aggressive
Moderator
Joined
Feb 15, 2014
Messages
17,844
Don't worry about "solving" it. If it's just the one bad sector, you can do nothing. If the errors start piling up, you'll really want to replace the drive.

In any case, you should have a spare burned in and ready to go.
 

HertogArjan

Dabbler
Joined
Oct 16, 2016
Messages
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So is it normal that a pending sector stays pending? Isn't it supposed to be reallocated? I do not like having this menacing 'critical' alert in the top right of the FreeNAS web interface.
 

Ericloewe

Not-very-passive-but-aggressive
Moderator
Joined
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Messages
17,844
So is it normal that a pending sector stays pending? Isn't it supposed to be reallocated?
The drive will take care of it at its own leisure. It's probably been remapped already for future writes.

? I do not like having this menacing 'critical' alert in the top right of the FreeNAS web interface.
That's the easy part. Uncheck the alert.
 

HertogArjan

Dabbler
Joined
Oct 16, 2016
Messages
30
If there's no read failure during the extended SMART test it's a false positive, it's quite common with WD disks, e.g.:

https://forums.freenas.org/index.php?posts/404270/

A false positive seems very likely, which is both good and bad news, since this would mean the health of the disk is fine but the 'phantom' pending sector will never disappear. I guess I'll just uncheck the alert like Ericloewe advised and be done with it.
 

Stux

MVP
Joined
Jun 2, 2016
Messages
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Scrubs only find errors when the error is in actual data.

You could offline the drive, and run bad blocks over it. If anything was going to 'fix' the drive, its that.

Probably a good idea actually.

Then you need to replace the offline drive with your newly wipes drive and let the data resilver.
 

Chris Moore

Hall of Famer
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Messages
10,085
Scrubs only find errors when the error is in actual data.

You could offline the drive, and run bad blocks over it. If anything was going to 'fix' the drive, its that.

Probably a good idea actually.

Then you need to replace the offline drive with your newly wipes drive and let the data resilver.
I had a similar situation and solved it with formatting the drive in another computer.
The pending sector just went away and the drive is reporting healthy.

Sent from my SAMSUNG-SGH-I537 using Tapatalk
 
Joined
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Messages
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Scrubs only find errors when the error is in actual data.

It's not just scrubbing, the extended SMART test passes without a read failure, this effectively means there are no pending sectors despite the one being reported.
 
Last edited:

HertogArjan

Dabbler
Joined
Oct 16, 2016
Messages
30
I had a similar situation and solved it with formatting the drive in another computer.
The pending sector just went away and the drive is reporting healthy.

I reformatted the drive in Windows, but the pending sector was still present afterwards.

You could offline the drive, and run bad blocks over it. If anything was going to 'fix' the drive, its that.

Probably a good idea actually.

Then you need to replace the offline drive with your newly wipes drive and let the data resilver.

In the end I offlined the drive, had written it with zeros and afterwards the pending sector had finally disappeared. No reallocated sector has popped up since either.

It seems very likely that the zero-fill eventually fixed the sector, but since the drive was reformatted before as well I can not say reformatting hasn't helped. If anyone happens to experience similiar issues and you have nothing else to try, completely rebuilding the drive seems to be a working fix.

Many thanks for all of the input!
 

Chris Moore

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Messages
10,085
I reformatted the drive in Windows, but the pending sector was still present afterwards.



In the end I offlined the drive, had written it with zeros and afterwards the pending sector had finally disappeared. No reallocated sector has popped up since either.

It seems very likely that the zero-fill eventually fixed the sector, but since the drive was reformatted before as well I can not say reformatting hasn't helped. If anyone happens to experience similiar issues and you have nothing else to try, completely rebuilding the drive seems to be a working fix.

Many thanks for all of the input!
I was not clear before. When I did the format that cleared up the pending sector, it was a "full" format, not a quick format. The quick only touches the first few blocks of the drive, where the full format writes to every sector.

Sent from my SAMSUNG-SGH-I537 using Tapatalk
 

Stux

MVP
Joined
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Messages
4,243
A badblocks run would've written to every sector 4 times.
 

farmerpling2

Patron
Joined
Mar 20, 2017
Messages
224
My experience with pending is when a bad block has been hardware CRC detected and could not be scrubbed clean. A write to it would cause it to be revectored, but none has occurred (i.e. R/O file, etc.)

It truly has lost data on that drive. Pull it out. I /dev/zero drive out, then bad_block scan it. Problem should be gone then...
 

HertogArjan

Dabbler
Joined
Oct 16, 2016
Messages
30
I was not clear before. When I did the format that cleared up the pending sector, it was a "full" format, not a quick format. The quick only touches the first few blocks of the drive, where the full format writes to every sector.

Sent from my SAMSUNG-SGH-I537 using Tapatalk

Thanks for the clarification, it does make sense that a long format would yield similiar results to a wipe.

Obviously, in most cases it would be preferable to wipe the drive in FreeNAS than to physically move/reconnect the drive to another system and perform a format there.

A badblocks run would've written to every sector 4 times.

Would you say there are any advantages of running the badblocks command in this case?

My experience with pending is when a bad block has been hardware CRC detected and could not be scrubbed clean. A write to it would cause it to be revectored, but none has occurred (i.e. R/O file, etc.)

It truly has lost data on that drive. Pull it out. I /dev/zero drive out, then bad_block scan it. Problem should be gone then...

By "/dev/zero drive out" you mean writing zeros to the disk? Doesn't the badblocks scan do that already?
 

Chris Moore

Hall of Famer
Joined
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Messages
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In my case, I had already removed the drive that had a pending sector and replace it with a spare. Then I put it in a Windows system to format it and do some testing to decide whether I was going to send it back on RMA.
In my case, the server was a production server, at my work and I didn't want to tie it up with testing, which is the reason I tested the drive in a different machine.

Sent from my SAMSUNG-SGH-I537 using Tapatalk
 
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