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question about S.M.A.R.T


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#1 etherjones

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Posted 15 August 2015 - 07:26 PM

.

 

Hello.

 

A friend was getting random long delays and freeze-ups on her laptop computer and dropped it off for me to check it out.

 

As is my standard procedure, the first thing I did was to boot a Memtest86+ CD and test the memory.  Two full passes and no errors.

 

The second thing I normally do is boot a S.M.A.R.T CD to tell the disk to do a self-test: smartctl -t short /dev/ada0

 

The disk failed the self-test, aborting with 90% of the disk remaining.

 

Now my question:  If a disk fails a smartctl self-test, does it mean that the disk has run out of reserve sectors, and so it can no longer "hide" errors from the outside world?  Or does it simply mean that the disk detected a bad sector and has now "quarantined" that sector, re-mapping it to a new sector from its reserve pool?   How can I tell when the disk has run out of reserve sectors?

 

.



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#2 etherjones

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Posted 16 August 2015 - 06:28 AM

 

Scanning an HDD with reallocated sectors will show the drive with all sectors ok only checking the HDD Smart information will show something like this S.M.A.R.T. Attribute: Reallocated Sectors Count and a related attribute Current Pending Sector Count

 

 

 

I'm trying to diagnose a Seagate ST9500325AS disk. Here are the SMART attributes:

SMART ATTRIBUTES:
 ID    Description                             Raw Value     Status        Value         Worst         Threshold     TEC                 
---------------------------------------------------------------------------------------------------------------------------------------------
  1    Raw Read Error Rate                     160272939     OK            117           77            6             N.A.                
  3    Spin Up Time                            0ms           OK            98            98            0             N.A.                
  4    Start/Stop Count                        4304          OK            96            96            20            N.A.                
  5    Reallocated Sector Count                0             OK            100           100           36            N.A.                
  7    Seek Error Rate                         77155012      OK            78            60            30            N.A.                
  9    Power On Time                           1586          OK            99            99            0             N.A.                
  A    Spin Retry Count                        0             OK            100           100           97            N.A.                
  C    Power Cycle Count                       4280          OK            96            96            20            N.A.                
 B8    (Unknown attribute)                     0             OK            100           100           99            N.A.                
 BB    (Unknown attribute)                     14876         OK            1             1             0             N.A.                
 BC    (Unknown attribute)                     19            OK            100           98            0             N.A.                
 BD    (Unknown attribute)                     0             OK            100           100           0             N.A.                
 BE    Temperature Difference from 100         572588066     OK            66            57            45            N.A.                
 BF    Gsense Error Rate                       86            OK            100           100           0             N.A.                
 C0    Power off Retract Count                 4             OK            100           100           0             N.A.                
 C1    Load/Unload Cycle Count                 28192         OK            86            86            0             N.A.                
 C2    Temperature                             34 C          OK            34            43            0             N.A.                
 C3    Hardware ECC Recovered                  160272939     OK            53            45            0             N.A.                
 C5    Current Pending Sector Count            1             OK            100           100           0             N.A.                
 C6    Uncorrectable Sector Count              1             OK            100           100           0             N.A.                
 C7    UltraDMA CRC Error Count                0             OK            200           200           0             N.A.                
 FE    (Unknown attribute)                     0             OK            100           100           0             N.A. 

The "Re-allocated Sector Count" is zero, and there is one "Current Pending Sector".

 

When I run Linux "badblocks -nsv /dev/sda" I get many bad blocks reported (the same ones each time I run it).  Why doesn't the disk re-map those bad blocks?

 

.



#3 SleepyDude

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Posted 16 August 2015 - 09:07 AM

Hi,

 

You should run a full scan using the Seagate tool called SeaTools. In the end of the scan the tool should ask you if you want to try remapping the bad sectors.

 

It seems this drive have 36 spare sectors.

 

 

5    Reallocated Sector Count                0             OK            100           100           36

 

I think that in certain conditions the "internal hdd controller" can detect and remap a bad sector during a read/write operation but I'm not sure. Using the manufacture specific tool is a better method and it also run other tests besides diagnosing bad sectors.

 

If other problems are found and the disk is under warranty the error code returned by the tool is needed to do an RMA process.


Edited by SleepyDude, 16 August 2015 - 09:28 AM.

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#4 etherjones

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Posted 16 August 2015 - 09:19 AM

Hi,

 

You should run a full scan using the Seagate tool called SeaTools. In the end of the scan the tool should ask you if you want to try remapping the bad sectors.

 

I created a bootable CD from SeaToolsDOS223ALL.ISO and booted it.   It did not detect my hard drive.  Which is very weird because every other bootable CD I have used so far  (Linux live, Clonezilla, SmartMonTools, Memtest86+) detects it.   And, of course, Windows boots from the hard disk.

 

It seems this drive have 3 spare sectors.

 

Where did you get "3" from ?

 

 

5    Reallocated Sector Count                0             OK            100           100           36

 



#5 SleepyDude

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Posted 16 August 2015 - 09:30 AM

Sorry I missed the 6!

 

The Dos version is old and sometimes doesn't see the HDD, try to change the Sata mode on the Bios from AHCI to IDE. Don't forget to change it back before booting windows or you will get a nice blue screen.


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#6 etherjones

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Posted 16 August 2015 - 02:26 PM

...try to change the Sata mode on the Bios from AHCI to IDE.

That worked, thanks for the tip.

 

I like how that software lets me write zero to just the one unrecoverable sector.  After doing that, smartctl -t short passes.

 

Presently running smartctl -t long (will take 140 minutes to complete)...

 

.



#7 etherjones

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Posted 19 August 2015 - 12:20 PM

Presently running smartctl -t long (will take 140 minutes to complete)...

 

thought I should post result:  smartctl -t long completed successfully.

 

Appended below are the current SMART attributes.

 

Observations:

 

- Uncorrectable Sector Count decremented from "1" to "0".

 

- Current Pending Sector Count decremented from "1" to "0"

 

- Reallocated Sector Count remained at "0"

 

Can anyone offer an informed explanation why the Reallocated Sector Count did not increment?

 ID    Description                             Raw Value     Status        Value         Worst         Threshold     TEC                 
---------------------------------------------------------------------------------------------------------------------------------------------
  1    Raw Read Error Rate                     64384333      OK            114           77            6             20 Sep 2015 12:44:12
  3    Spin Up Time                            0ms           OK            98            98            0             N.A.                
  4    Start/Stop Count                        4325          OK            96            96            20            N.A.                
  5    Reallocated Sector Count                0             OK            100           100           36            N.A.                
  7    Seek Error Rate                         77989535      OK            78            60            30            N.A.                
  9    Power On Time                           1615          OK            99            99            0             N.A.                
  A    Spin Retry Count                        0             OK            100           100           97            N.A.                
  C    Power Cycle Count                       4301          OK            96            96            20            N.A.                
 B8    (Unknown attribute)                     0             OK            100           100           99            N.A.                
 BB    (Unknown attribute)                     14985         OK            1             1             0             N.A.                
 BC    (Unknown attribute)                     19            OK            100           98            0             N.A.                
 BD    (Unknown attribute)                     0             OK            100           100           0             N.A.                
 BE    Temperature Difference from 100         538640416     OK            68            57            45            N.A.                
 BF    Gsense Error Rate                       86            OK            100           100           0             N.A.                
 C0    Power off Retract Count                 4             OK            100           100           0             N.A.                
 C1    Load/Unload Cycle Count                 28381         OK            86            86            0             N.A.                
 C2    Temperature                             32 C          OK            32            43            0             N.A.                
 C3    Hardware ECC Recovered                  64384333      OK            55            44            0             N.A.                
 C5    Current Pending Sector Count            0             OK            100           100           0             N.A.                
 C6    Uncorrectable Sector Count              0             OK            100           100           0             N.A.                
 C7    UltraDMA CRC Error Count                0             OK            200           200           0             N.A.                
 FE    (Unknown attribute)                     0             OK            100           100           0             N.A. 


#8 SleepyDude

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Posted 20 August 2015 - 03:37 AM

Eventually the HardDisk recheck the sector and didn't find any problem this time!

 

From http://www.dposoft.net/hdd.html

 

How it works

Almost 60% of all hard drives damaged with bad sectors have an incorrectly magnetized disk surface. We have developed an algorithm which is used to repair damaged disk surfaces. This technology is hardware independent, it supports many types of hard drives and repairs damage that even low-level disk formatting cannot repair. As a result, previously unreadable information will be restored. Because of the way the repair is made, the existing information on the disk drive will not be affected!

 

If the software can do this I think the controller on the drive can also do it in some cases...


Edited by SleepyDude, 20 August 2015 - 03:37 AM.

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#9 UPI

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Posted 29 August 2015 - 06:53 AM

sector reallocation works like this:

 

- sector can not be read (uncorrectable) > becomes pending reallocation

- sector is only reallocated when written to, this is how the various zero fillers work.

 

And this how spinrite works. It tries to read the sector many times, and often the sector can be read a few times, It compares the data from those reads and makes a best guess. The best guess is written to that sector. Which the disk does not do, instead it writes it t a spare sector. In such an event you would normally see the raw value for pending sectors go down one, and reallocated raw value increase by one. It's probably how the dpo software works as well. In between the actual data and what ends up being written on the disk are so many layers of encoding and what not, that it is impossible to come up with some magic magnetic pattern, that's the snake oil part.

 

I can't explain the pending being zero as well as the reallocated raw value. Only reason could be that now the disk was able to read the sector.

 

One last remark. The 36 value is not the actual number of spares for this disk. This is not a raw value.

 

- Joep






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