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贴一个关于BadBlockHowTo的摘录，但本人功力不够，继续学习
THIS DOCUMENT SHOWS HOW TO IDENTIFY THE FILE ASSOCIATED WITH AN
UNREADABLE DISK SECTOR, AND HOW TO FORCE THAT SECTOR TO REALLOCATE.
Assumptions: Linux OS, ext2 or ext3 file system.
Bruce Allen <smartmontools-support@lists.sourceforge.net>
Thanks to Sergey Vlasov, Theodore Ts'o, Michael Bendzick, and others
for explaining this to me. I would like to add text showing how to do
this for other file systems, in particular ReiserFS, XFS, and JFS:
please email me if you can provide this information.
NOTE: Starting with GNU coreutils release 5.3.0, dd on Linux includes
options 'iflag=direct' and 'oflag=direct'. Using these with the dd commands
below should be helpful, because adding these flags should avoid any interaction
with the block buffering IO layer in Linux and permit direct reads/writes
from the raw device. Use 'dd --help' to see if your version of dd supports
these options. If not, build the latest code from
fttp://alpha.gnu.org/gnu/coreutils.
In this example, the disk is failing self-tests at Logical Block
Address LBA = 0x016561e9 = 23421417. The LBA counts sectors in units
of 512 bytes, and starts at zero.
-----------------------------------------------------------------------------------------------
root]# smartctl -l selftest /dev/hda:
SMART Self-test log structure revision number 1
Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error
# 1 Extended offline Completed: read failure 90% 217 0x016561e9
-----------------------------------------------------------------------------------------------
Note that other signs that there is a bad sector on the disk can be
found in the non-zero value of the Current Pending Sector count:
-----------------------------------------------------------------------------------------------
root]# smartctl -A /dev/hda
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
5 Reallocated_Sector_Ct 0x0033 100 100 005 Pre-fail Always - 0
196 Reallocated_Event_Count 0x0032 100 100 000 Old_age Always - 0
197 Current_Pending_Sector 0x0022 100 100 000 Old_age Always - 1
198 Offline_Uncorrectable 0x0008 100 100 000 Old_age Offline - 1
-----------------------------------------------------------------------------------------------
First Step: We need to locate the partition on which this sector of
the disk lives:
-----------------------------------------------------------------------------------------------
root]# fdisk -lu /dev/hda
Disk /dev/hda: 123.5 GB, 123522416640 bytes
255 heads, 63 sectors/track, 15017 cylinders, total 241254720 sectors
Units = sectors of 1 * 512 = 512 bytes
Device Boot Start End Blocks Id System
/dev/hda1 * 63 4209029 2104483+ 83 Linux
/dev/hda2 4209030 5269319 530145 82 Linux swap
/dev/hda3 5269320 238227884 116479282+ 83 Linux
/dev/hda4 238227885 241248104 1510110 83 Linux
-----------------------------------------------------------------------------------------------
The partition /dev/hda3 starts at LBA 5269320 and extends past the
'problem' LBA. The 'problem' LBA is offset 23421417 - 5269320 =
18152097 sectors into the partition /dev/hda3.
To verify the type of the file system and the mount point, look in
/etc/fstab:
-----------------------------------------------------------------------------------------------
root]# grep hda3 /etc/fstab
/dev/hda3 /data ext2 defaults 1 2
-----------------------------------------------------------------------------------------------
You can see that this is an ext2 file system, mounted at /data.
Second Step: we need to find the blocksize of the file system
(normally 4096 bytes for ext2):
-----------------------------------------------------------------------------------------------
root]# tune2fs -l /dev/hda3 | grep Block
Block count: 29119820
Block size: 4096
-----------------------------------------------------------------------------------------------
In this case the block size is 4096 bytes.
Third Step: we need to determine which File System Block contains this
LBA. The formula is:
b = (int)((L-S)*512/B)
where:
b = File System block number
B = File system block size in bytes
L = LBA of bad sector
S = Starting sector of partition as shown by fdisk -lu
and (int) denotes the integer part.
In our example, L=23421417, S=5269320, and B=4096. Hence the
'problem' LBA is in block number
b = (int)18152097*512/4096 = (int)2269012.125
so b=2269012.
Note: the fractional part of 0.125 indicates that this problem LBA is
actually the second of the eight sectors that make up this file system
block.
Fourth Step: we use debugfs to locate the inode stored in this block,
and the file that contains that inode:
-----------------------------------------------------------------------------------------------
root]# debugfs
debugfs 1.32 (09-Nov-2002)
debugfs: open /dev/hda3
debugfs: icheck 2269012
Block Inode number
2269012 41032
debugfs: ncheck 41032
Inode Pathname
41032 /S1/R/H/714197568-714203359/H-R-714202192-16.gwf
-----------------------------------------------------------------------------------------------
In this example, you can see that the problematic file (with the mount
point included in the path) is:
/data/S1/R/H/714197568-714203359/H-R-714202192-16.gwf
To force the disk to reallocate this bad block we'll write zeros to
the bad block, and sync the disk:
-----------------------------------------------------------------------------------------------
root]# dd if=/dev/zero of=/dev/hda3 bs=4096 count=1 seek=2269012
root]# sync
-----------------------------------------------------------------------------------------------
NOTE: THIS LAST STEP HAS PERMANENTLY AND IRRETREVIABLY DESTROYED SOME
OF THE DATA THAT WAS IN THIS FILE. DON'T DO THIS UNLESS YOU DON'T
NEED THE FILE OR YOU CAN REPLACE IT WITH A FRESH OR CORRECT VERSION.
Now everything is back to normal: the sector has been reallocated.
Compare the output just below to similar output near the top of this
article:
-----------------------------------------------------------------------------------------------
root]# smartctl -A /dev/hda
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
5 Reallocated_Sector_Ct 0x0033 100 100 005 Pre-fail Always - 1
196 Reallocated_Event_Count 0x0032 100 100 000 Old_age Always - 1
197 Current_Pending_Sector 0x0022 100 100 000 Old_age Always - 0
198 Offline_Uncorrectable 0x0008 100 100 000 Old_age Offline - 1
-----------------------------------------------------------------------------------------------
Note: for some disks it may be necessary to update the SMART Attribute values by using
smartctl -t offline /dev/hda
The disk now passes its self-tests again:
----------------------------------------------------------------------------------------------- |
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发表于 2005-11-27 12:54