最後更新: 2019-10-15

介紹

Bad blocks <- 一些 read 唔到的 sector

 

A modern disk handles bad sectors internally (transparently remapping)

those sectors from a reserved set of sectors during writes.

目錄

• badblock
• filefrag
• Print block device size
• Identification of HDD by SATA port number

 

---

badblock - 對 File System 進行測試

 

[方式1] 強制 fsck 進行 badblock 檢查

fsck -fc /dev/sda

e2fsck 1.41.3 (12-Oct-2008)
Checking for bad blocks (read-only test):   9.25% done, 2:04 elapsed

[方式1] badblocks Bad sector 測試

對 partion 進行 read 測試

smartctl -i /dev/sde | grep Sizes        # Sector Sizes:  512 bytes logical, 4096 bytes physica

badblocks -v -s -b 4096 /dev/sda1

• -v                      # Verbose mode.
• -s                      # Show the progress of the scan by writing out rough percentage
• -b block-size      # Specify the size of blocks in bytes.  The default is 1024 byte
• -p num_passes   # test 多小次 (Default is 0)

Output

Checking blocks 0 to 96255
Checking for bad blocks (read-only test):  58.11% done, 0:01 elapsed

對 umount 了的 partion 進行 read+write 測試

# -n                      Use non-destructive "read-write" mode.

badblocks -s -n /dev/sda1

Checking for bad blocks (non-destructive read-write test)
Testing with random pattern:  31.52% done, 0:03 elapsed

Checking for bad blocks (non-destructive read-write test)
Testing with random pattern: done

P.S.

A non-destructive read-write test (-n) makes a backup of the original content of a sector before testing and

then restoring the content from the backup.

破壞性 Read/Write Test

它一共有兩個步驟. 先係 write, 之後就 read

# -w                     Use write-mode test. 破壞性的 (write patterns: 0xaa)

badblocks -v -s -w /dev/sdd

Checking for bad blocks in read-write mode
From block 0 to 1465138583
Testing with pattern 0xaa: done
Reading and comparing:  46.60% done, 19:58:22 elapsed. (0/0/0 errors)

 

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filefrag - 查看檔案的 fragment 情況

 

filefrag winxp.sp3-ide8g.idv

winxp.sp3-ide8g.idv: 13 extents found

filefrag -v winxp.sp3-ide8g.idv

Filesystem type is: ef53
File size of winxp.sp3-ide8g.idv is 4694508032 (1146121 blocks, blocksize 4096)
Discontinuity: Block 16 is at 2545216 (was 4754073)
Discontinuity: Block 10240 is at 2555904 (was 2555440)
Discontinuity: Block 75776 is at 2656256 (was 2621440)
Discontinuity: Block 565248 is at 3178496 (was 3145728)
Discontinuity: Block 894976 is at 4472832 (was 3508224)
Discontinuity: Block 1017856 is at 4601856 (was 4595712)
Discontinuity: Block 1020169 is at 11300 (was 4604169)
Discontinuity: Block 1040384 is at 382976 (was 31515)
Discontinuity: Block 1132544 is at 477184 (was 475136)
Discontinuity: Block 1142784 is at 499712 (was 487424)
Discontinuity: Block 1144832 is at 505856 (was 501760)
Discontinuity: Block 1145865 is at 31515 (was 506889)
winxp.sp3-ide8g.idv: 13 extents found

 

---

Print block device size

 

blockdev --getsize64 /dev/sda returns size in bytes.

fdisk -l /dev/sda

lsblk | grep sda

 

---

Identification of HDD by SATA port number

 

lshw -c storage -c disk

  *-scsi:0
       physical id: 1
       logical name: scsi2
       capabilities: emulated
     *-disk
          description: ATA Disk
          product: ST500DM002-1BC14
          vendor: Seagate
          physical id: 0.1.0
          bus info: scsi@2:0.1.0
          logical name: /dev/sda
          version: JC4B
          serial: S2A38N69
          size: 465GiB (500GB)
          capabilities: partitioned partitioned:dos
          configuration: ansiversion=5 logicalsectorsize=512 sectorsize=512 signature=0000440f

 

---

遇上 Bad Sector

 

dmesg

... ata1.00: exception Emask 0x0 SAct 0x10000000 SErr 0x0 action 0x0
... ata1.00: irq_stat 0x40000008
... ata1.00: failed command: READ FPDMA QUEUED
... ata1.00: cmd 60/08:e0:30:bd:88/00:00:14:00:00/40 tag 28 ncq dma 4096 in
...          res 51/40:38:00:00:00/00:00:00:00:00/00 Emask 0x409 (media error) <F>
... ata1.00: status: { DRDY ERR }
... ata1.00: error: { UNC }
... ata1.00: configured for UDMA/133
... sd 0:0:0:0: [sda] tag#28 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE cmd_age=0s
... sd 0:0:0:0: [sda] tag#28 Sense Key : Medium Error [current]
... sd 0:0:0:0: [sda] tag#28 Add. Sense: Unrecovered read error - auto reallocate failed
... sd 0:0:0:0: [sda] tag#28 CDB: Read(10) 28 00 14 88 bd 30 00 00 08 00
... blk_update_request: I/O error, dev sda, sector 344505648 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
... Buffer I/O error on dev sda, logical block 43063206, async page read
... ata1: EH complete

smartctl -A /dev/sda | grep -e Reallocated -e Uncorrectable_Error_Cnt

  5 Reallocated_Sector_Ct   0x0033   100   100   010    Pre-fail  Always       -       0
160 Uncorrectable_Error_Cnt 0x0032   100   100   050    Old_age   Always       -       0
196 Reallocated_Event_Count 0x0032   100   100   000    Old_age   Always       -       0

在 read 情況不會 remap sector, 這情況一共有兩個方案

1. 在 FS level remap 佢

2. write 一次那 block 去 trigger remap

# 查看 socker size

hdparm -I /dev/sda | grep 'Sector size'

        Logical  Sector size:                   512 bytes
        Physical Sector size:                   512 bytes

# 4k (bs=512 count=8) (344505648 -> 344505655)      # 心得: 有問題時, 多數是 4k size 出事.

dd if=/dev/sda of=/dev/null bs=512 count=8 skip=344505648

dd: error reading '/dev/sda': Input/output error

hdparm (completely bypassing the usual block layer read/write mechanisms)

# hdparm will issue a low-level read for  the specified sector.

hdparm --read-sector 344505648 /dev/sda

/dev/sda:
reading sector 344505648: SG_IO: bad/missing sense data, sb[]:  ...
succeeded
...

# hdparm will issue a low-level write zeros to the specified sector.

# --yes-i-know-what-i-am-doing

hdparm --write-sector 344505648 /dev/sda

/dev/sda:
re-writing sector 344505648: succeeded