[smartmontools-support] pending sector: bad blocks howto doesnt work

[Juergen B. <Jue...@we...>]

I use debian lenny on my system and have enabled smartmon testing. For some days now 
I receive emails telling me that there are pending sectors:

Device: /dev/sda, 1 Offline uncorrectable sectors

Thus, I read the 'Bad block HOWTO for smartmontools' and tried to correct the problem. 
However, it does not work. Here is what I did:

I listed the selftest errors inorder to find out the bad block:

> lisa:/home/jba/comp/hardware/harddisks/HD103UI# smartctl -l selftest /dev/sda
> smartctl version 5.38 [i686-pc-linux-gnu] Copyright (C) 2002-8 Bruce Allen
> Home page is http://smartmontools.sourceforge.net/
> 
> === START OF READ SMART DATA SECTION ===
> SMART Self-test log structure revision number 1
> Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
> # 1  Short offline       Completed: read failure       20%      2363         1116720298
> # 2  Short offline       Completed: read failure       20%      2351         1116720298
> # 3  Short offline       Completed without error       00%      2329         -
> ...

Ok, error is on LBA 1116720298. I then looked into fdisk to find out, to which partition 
the LBA belongs:

> lisa:/home/jba/comp/hardware/harddisks/HD103UI# fdisk -lu /dev/sda
> 
> Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
> 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
> Units = sectors of 1 * 512 = 512 bytes
> Disk identifier: 0x000da0a1
> 
>    Device Boot      Start         End      Blocks   Id  System
> /dev/sda1   *          63    78140159    39070048+   c  W95 FAT32 (LBA)
> /dev/sda2        78140160    82060019     1959930   82  Linux swap / Solaris
> /dev/sda3        82060020   199270259    58605120   83  Linux
> /dev/sda4       199270260  1953520064   877124902+   5  Extended
> /dev/sda5       199270323  1566466019   683597848+  83  Linux
> /dev/sda6      1566466083  1953520064   193526991   83  Linux

The bad LBA is in sda5. The I looked for the block size:

> lisa:/home/jba/comp/hardware/harddisks/HD103UI# tune2fs -l /dev/sda5 | grep Block
> Block count:              170899462
> Block size:               4096
> Blocks per group:         32768

Block size is 4096. Thus, the bad block calulates as

b = (int)((L-S)*512/B)  = (int) (1116720298 - 199270323) * 512 / 4096 = (int) 114681246.88 = 114681246

This should be the block number.

> lisa:/home/jba/comp/hardware/harddisks/HD103UI# debugfs
> debugfs 1.41.3 (12-Oct-2008)
> debugfs:  open /dev/sda5
> debugfs:  icheck 114681246
> Block   Inode number
> 114681246       <block not found>

But debugfs does not find a corresponding Inode for this block. What does this mean?

It seems that the buggy sector isnt used at all. But why does smart report an error then? 
Could it be, that the block was used before for, but the file was erased in the meantime?

What shoul I do? just overwriting the block with dd (dd if=/dev/zero of=/dev/hda3 bs=4096 count=1 seek=114681246)?

Juergen










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