2

Some days ago I found that the partition related to my RAID 5 wasn't mounted. I examined my disks and I got:

mdadm --examine /dev/sd{a,b,c,d}1

mdadm: No md superblock detected on /dev/sda1.

/dev/sdb1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : 87fdc598:a995d0f7:41123bcf:e2760aeb
           Name : itake:0  (local to host itake)
  Creation Time : Tue Aug 28 17:44:52 2012
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 1953122952 (931.32 GiB 1000.00 GB)
     Array Size : 2929683456 (2793.96 GiB 3000.00 GB)
  Used Dev Size : 1953122304 (931.32 GiB 1000.00 GB)
    Data Offset : 2048 sectors
   Super Offset : 8 sectors
   Unused Space : before=1968 sectors, after=648 sectors
          State : clean
    Device UUID : db15e0ad:ef9f28be:de5e5a5a:f929ebb9

    Update Time : Sun Sep 11 00:00:26 2016
       Checksum : 700e7a14 - correct
         Events : 6141

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 1
   Array State : AA.A ('A' == active, '.' == missing, 'R' == replacing)


/dev/sdc1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : 87fdc598:a995d0f7:41123bcf:e2760aeb
           Name : itake:0  (local to host itake)
  Creation Time : Tue Aug 28 17:44:52 2012
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 1953122952 (931.32 GiB 1000.00 GB)
     Array Size : 2929683456 (2793.96 GiB 3000.00 GB)
  Used Dev Size : 1953122304 (931.32 GiB 1000.00 GB)
    Data Offset : 2048 sectors
   Super Offset : 8 sectors
   Unused Space : before=1968 sectors, after=648 sectors
          State : clean
    Device UUID : f3c74ca8:076e5078:305ad83b:159f048d

    Update Time : Sun Sep  4 00:08:53 2016
       Checksum : d9306794 - correct
         Events : 5896

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 2
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)


/dev/sdd1:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x0
     Array UUID : 87fdc598:a995d0f7:41123bcf:e2760aeb
           Name : itake:0  (local to host itake)
  Creation Time : Tue Aug 28 17:44:52 2012
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 1953122952 (931.32 GiB 1000.00 GB)
     Array Size : 2929683456 (2793.96 GiB 3000.00 GB)
  Used Dev Size : 1953122304 (931.32 GiB 1000.00 GB)
    Data Offset : 2048 sectors
   Super Offset : 8 sectors
   Unused Space : before=1968 sectors, after=648 sectors
          State : clean
    Device UUID : 4b376772:29ca4f41:342d39df:877fece0

    Update Time : Sun Sep 11 00:00:26 2016
       Checksum : 639ce9a5 - correct
         Events : 6141

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 3
   Array State : AA.A ('A' == active, '.' == missing, 'R' == replacing)  

So I thought that only sda was damaged and I could recover the information. I bought a new disk and now I saw that it wasn't sda only but sdc as well. I wonder if there is any chance of try to repair any of two disks to try to recreate and recover the information before replace both...

I leave here some useful information about the errors, if you need something else please let me know

cat /proc/mdstat

Personalities : [raid6] [raid5] [raid4]
unused devices: <none>  

cat /var/log/syslog

Nov 11 09:16:59 itake kernel: [   18.230695] sd 0:0:0:0: [sda] Unhandled sense code
Nov 11 09:16:59 itake kernel: [   18.230698] sd 0:0:0:0: [sda]  Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Nov 11 09:16:59 itake kernel: [   18.230703] sd 0:0:0:0: [sda]  Sense Key : Medium Error [current] [descriptor]
Nov 11 09:16:59 itake kernel: [   18.230708] Descriptor sense data with sense descriptors (in hex):
Nov 11 09:16:59 itake kernel: [   18.230711]         72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
Nov 11 09:16:59 itake kernel: [   18.230721]         00 00 08 08
Nov 11 09:16:59 itake kernel: [   18.230726] sd 0:0:0:0: [sda]  Add. Sense: Unrecovered read error - auto reallocate failed
Nov 11 09:16:59 itake kernel: [   18.230734] sd 0:0:0:0: [sda] CDB: Read(10): 28 00 00 00 08 08 00 00 08 00
Nov 11 09:16:59 itake kernel: [   18.230744] end_request: I/O error, dev sda, sector 2056
Nov 11 09:16:59 itake kernel: [   18.230796] Buffer I/O error on device sda1, logical block 1
Nov 11 09:16:59 itake kernel: [   18.230881] ata1: EH complete

...

Nov 11 09:16:59 itake kernel: [  104.221334] sd 2:0:0:0: [sdc] Unhandled sense code
Nov 11 09:16:59 itake kernel: [  104.221337] sd 2:0:0:0: [sdc]  Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Nov 11 09:16:59 itake kernel: [  104.221342] sd 2:0:0:0: [sdc]  Sense Key : Medium Error [current] [descriptor]
Nov 11 09:16:59 itake kernel: [  104.221347] Descriptor sense data with sense descriptors (in hex):
Nov 11 09:16:59 itake kernel: [  104.221350]         72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
Nov 11 09:16:59 itake kernel: [  104.221360]         74 70 68 00
Nov 11 09:16:59 itake kernel: [  104.221365] sd 2:0:0:0: [sdc]  Add. Sense: Unrecovered read error - auto reallocate failed
Nov 11 09:16:59 itake kernel: [  104.221372] sd 2:0:0:0: [sdc] CDB: Read(10): 28 00 74 70 68 00 00 01 d0 00
Nov 11 09:16:59 itake kernel: [  104.221381] end_request: I/O error, dev sdc, sector 1953523712
Nov 11 09:16:59 itake kernel: [  104.221431] Buffer I/O error on device sdc, logical block 244190464
Nov 11 09:16:59 itake kernel: [  104.221482] Buffer I/O error on device sdc, logical block 244190465
Nov 11 09:16:59 itake kernel: [  104.221524] Buffer I/O error on device sdc, logical block 244190466
Nov 11 09:16:59 itake kernel: [  104.221567] Buffer I/O error on device sdc, logical block 244190467
Nov 11 09:16:59 itake kernel: [  104.221608] Buffer I/O error on device sdc, logical block 244190468
Nov 11 09:16:59 itake kernel: [  104.221649] Buffer I/O error on device sdc, logical block 244190469
Nov 11 09:16:59 itake kernel: [  104.221690] Buffer I/O error on device sdc, logical block 244190470
Nov 11 09:16:59 itake kernel: [  104.221731] Buffer I/O error on device sdc, logical block 244190471
Nov 11 09:16:59 itake kernel: [  104.221772] Buffer I/O error on device sdc, logical block 244190472
Nov 11 09:16:59 itake kernel: [  104.221813] Buffer I/O error on device sdc, logical block 244190473
Nov 11 09:16:59 itake kernel: [  104.221897] ata3: EH complete
Nov 11 09:16:59 itake kernel: [  107.652344] ata3.00: exception Emask 0x0 SAct 0x7 SErr 0x0 action 0x0
Nov 11 09:16:59 itake kernel: [  107.652389] ata3.00: irq_stat 0x40000008
Nov 11 09:16:59 itake kernel: [  107.652429] ata3.00: failed command: READ FPDMA QUEUED
Nov 11 09:16:59 itake kernel: [  107.652474] ata3.00: cmd 60/08:00:d8:69:70/00:00:74:00:00/40 tag 0 ncq 4096 in
Nov 11 09:16:59 itake kernel: [  107.652476]          res 41/40:00:d8:69:70/00:00:74:00:00/40 Emask 0x409 (media error) <F>
Nov 11 09:16:59 itake kernel: [  107.652559] ata3.00: status: { DRDY ERR }
Nov 11 09:16:59 itake kernel: [  107.652598] ata3.00: error: { UNC }
Nov 11 09:16:59 itake kernel: [  107.654733] ata3.00: configured for UDMA/133
Nov 11 09:16:59 itake kernel: [  107.654754] ata3: EH complete


...

Nov 11 09:16:59 itake kernel: [  137.768972] sd 0:0:0:0: [sda]  Add. Sense: Unrecovered read error - auto reallocate failed
Nov 11 09:16:59 itake kernel: [  137.768979] sd 0:0:0:0: [sda] CDB: Read(10): 28 00 00 00 08 08 00 00 08 00
Nov 11 09:16:59 itake kernel: [  137.768989] end_request: I/O error, dev sda, sector 2056
Nov 11 09:16:59 itake kernel: [  137.769067] ata1: EH complete
Nov 11 09:16:59 itake kernel: [  137.779624] md: md0 stopped.
Nov 11 09:16:59 itake kernel: [  138.630989] ata3.00: exception Emask 0x0 SAct 0x3 SErr 0x0 action 0x0
Nov 11 09:16:59 itake kernel: [  138.631035] ata3.00: irq_stat 0x40000008
Nov 11 09:16:59 itake kernel: [  138.631076] ata3.00: failed command: READ FPDMA QUEUED
Nov 11 09:16:59 itake kernel: [  138.631121] ata3.00: cmd 60/08:00:40:68:70/00:00:74:00:00/40 tag 0 ncq 4096 in
Nov 11 09:16:59 itake kernel: [  138.631123]          res 41/40:00:40:68:70/00:00:74:00:00/40 Emask 0x409 (media error) <F>
Nov 11 09:16:59 itake kernel: [  138.631206] ata3.00: status: { DRDY ERR }
Nov 11 09:16:59 itake kernel: [  138.631245] ata3.00: error: { UNC }
Nov 11 09:16:59 itake kernel: [  138.633417] ata3.00: configured for UDMA/133
Nov 11 09:16:59 itake kernel: [  138.633443] ata3: EH complete
Nov 11 09:16:59 itake kernel: [  138.637684] md: bind<sdc1>
Nov 11 09:16:59 itake kernel: [  138.637896] md: bind<sdd1>
Nov 11 09:16:59 itake kernel: [  138.638139] md: bind<sdb1>
Nov 11 09:16:59 itake kernel: [  138.638173] md: kicking non-fresh sdc1 from array!
Nov 11 09:16:59 itake kernel: [  138.638180] md: unbind<sdc1>
Nov 11 09:16:59 itake kernel: [  138.640178] md: export_rdev(sdc1)
Nov 11 09:16:59 itake kernel: [  138.640178] md: export_rdev(sdc1)
Nov 11 09:16:59 itake kernel: [  138.708065] raid6: int64x1   1355 MB/s
Nov 11 09:16:59 itake kernel: [  138.776062] raid6: int64x2   1504 MB/s
Nov 11 09:16:59 itake kernel: [  138.844062] raid6: int64x4   1284 MB/s
Nov 11 09:16:59 itake kernel: [  138.912061] raid6: int64x8   1109 MB/s
Nov 11 09:16:59 itake kernel: [  138.980085] raid6: sse2x1    2124 MB/s
Nov 11 09:16:59 itake kernel: [  139.048065] raid6: sse2x2    3413 MB/s
Nov 11 09:16:59 itake kernel: [  139.116061] raid6: sse2x4    4022 MB/s
Nov 11 09:16:59 itake kernel: [  139.116064] raid6: using algorithm sse2x4 (4022 MB/s)
Nov 11 09:16:59 itake kernel: [  139.116302] async_tx: api initialized (async)
Nov 11 09:16:59 itake kernel: [  139.116471] xor: automatically using best checksumming function: generic_sse
Nov 11 09:16:59 itake kernel: [  139.136056]    generic_sse:  6183.000 MB/sec
Nov 11 09:16:59 itake kernel: [  139.136059] xor: using function: generic_sse (6183.000 MB/sec)
Nov 11 09:16:59 itake kernel: [  139.137667] md: raid6 personality registered for level 6
Nov 11 09:16:59 itake kernel: [  139.137671] md: raid5 personality registered for level 5
Nov 11 09:16:59 itake kernel: [  139.137674] md: raid4 personality registered for level 4
Nov 11 09:16:59 itake kernel: [  139.137936] bio: create slab <bio-1> at 1
Nov 11 09:16:59 itake kernel: [  139.137960] md/raid:md0: device sdb1 operational as raid disk 1
Nov 11 09:16:59 itake kernel: [  139.137964] md/raid:md0: device sdd1 operational as raid disk 3
Nov 11 09:16:59 itake kernel: [  139.138427] md/raid:md0: allocated 4280kB
Nov 11 09:16:59 itake kernel: [  139.138551] md/raid:md0: not enough operational devices (2/4 failed)
Nov 11 09:16:59 itake kernel: [  139.138628] RAID conf printout:
Nov 11 09:16:59 itake kernel: [  139.138630]  --- level:5 rd:4 wd:2
Nov 11 09:16:59 itake kernel: [  139.138634]  disk 1, o:1, dev:sdb1
Nov 11 09:16:59 itake kernel: [  139.138637]  disk 3, o:1, dev:sdd1
Nov 11 09:16:59 itake kernel: [  139.139106] md/raid:md0: failed to run raid set.
Nov 11 09:16:59 itake kernel: [  139.139146] md: pers->run() failed ...
Nov 11 09:16:59 itake kernel: [  139.139523] md: md0 stopped.
Nov 11 09:16:59 itake kernel: [  139.139532] md: unbind<sdb1>
Nov 11 09:16:59 itake kernel: [  139.156130] md: export_rdev(sdb1)
Nov 11 09:16:59 itake kernel: [  139.156158] md: unbind<sdd1>
Nov 11 09:16:59 itake kernel: [  139.168118] md: export_rdev(sdd1)

...

smartctl -a /dev/sda

smartctl 6.5 2016-01-24 r4214 [x86_64-linux-3.2.0-4-amd64] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     SAMSUNG SpinPoint F3
Device Model:     SAMSUNG HD103SJ
Serial Number:    S246J1KZ410348
LU WWN Device Id: 5 0024e9 0034ebb37
Firmware Version: 1AJ10001
User Capacity:    1,000,203,804,160 bytes [1.00 TB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    7200 rpm
Form Factor:      3.5 inches
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ATA8-ACS T13/1699-D revision 6
SATA Version is:  SATA 2.6, 3.0 Gb/s
Local Time is:    Fri Nov 11 11:17:00 2016 CET
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:      ( 121) The previous self-test completed having
                    the read element of the test failed.
Total time to complete Offline
data collection:        ( 9300) seconds.
Offline data collection
capabilities:            (0x5b) SMART execute Offline immediate.
                    Auto Offline data collection on/off support.
                    Suspend Offline collection upon new
                    command.
                    Offline surface scan supported.
                    Self-test supported.
                    No 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:    ( 155) minutes.
SCT capabilities:          (0x003f) 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   100   100   051    Pre-fail  Always       -       784
  2 Throughput_Performance  0x0026   252   252   000    Old_age   Always       -       0
  3 Spin_Up_Time            0x0023   070   069   025    Pre-fail  Always       -       9385
  4 Start_Stop_Count        0x0032   099   099   000    Old_age   Always       -       1225
  5 Reallocated_Sector_Ct   0x0033   252   252   010    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x002e   252   252   051    Old_age   Always       -       0
  8 Seek_Time_Performance   0x0024   252   252   015    Old_age   Offline      -       0
  9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       30077
 10 Spin_Retry_Count        0x0032   252   252   051    Old_age   Always       -       0
 11 Calibration_Retry_Count 0x0032   252   252   000    Old_age   Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       212
191 G-Sense_Error_Rate      0x0022   252   252   000    Old_age   Always       -       0
192 Power-Off_Retract_Count 0x0022   252   252   000    Old_age   Always       -       0
194 Temperature_Celsius     0x0002   064   052   000    Old_age   Always       -       21 (Min/Max 11/48)
195 Hardware_ECC_Recovered  0x003a   100   100   000    Old_age   Always       -       0
196 Reallocated_Event_Count 0x0032   252   252   000    Old_age   Always       -       0
197 Current_Pending_Sector  0x0032   100   100   000    Old_age   Always       -       2
198 Offline_Uncorrectable   0x0030   252   252   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x0036   200   200   000    Old_age   Always       -       0
200 Multi_Zone_Error_Rate   0x002a   100   100   000    Old_age   Always       -       64
223 Load_Retry_Count        0x0032   252   252   000    Old_age   Always       -       0
225 Load_Cycle_Count        0x0032   100   100   000    Old_age   Always       -       1244

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  Short offline       Completed: read failure       90%     30077         2056
# 2  Extended offline    Completed: read failure       90%     30077         2056

SMART Selective self-test log data structure revision number 0
Note: revision number not 1 implies that no selective self-test has ever been run
 SPAN  MIN_LBA  MAX_LBA  CURRENT_TEST_STATUS
    1        0        0  Completed_read_failure [90% left] (0-65535)
    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.

smartctl -a /dev/sdc

smartctl 6.5 2016-01-24 r4214 [x86_64-linux-3.2.0-4-amd64] (local build)
Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Family:     Western Digital Green
Device Model:     WDC WD10EZRX-00A8LB0
Serial Number:    WD-WMC1U5433779
LU WWN Device Id: 5 0014ee 657f09173
Firmware Version: 01.01A01
User Capacity:    1,000,204,886,016 bytes [1.00 TB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ATA8-ACS (minor revision not indicated)
SATA Version is:  SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s)
Local Time is:    Fri Nov 11 11:17:08 2016 CET
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:  (0x85) Offline data collection activity
                    was aborted by an interrupting command from host.
                    Auto Offline Data Collection: Enabled.
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:        (12960) 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:    ( 148) minutes.
Conveyance self-test routine
recommended polling time:    (   5) minutes.
SCT capabilities:          (0x30b5) SCT Status 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       -       6787
  3 Spin_Up_Time            0x0027   139   137   021    Pre-fail  Always       -       4041
  4 Start_Stop_Count        0x0032   096   096   000    Old_age   Always       -       4454
  5 Reallocated_Sector_Ct   0x0033   171   171   140    Pre-fail  Always       -       1262
  7 Seek_Error_Rate         0x002e   200   200   000    Old_age   Always       -       0
  9 Power_On_Hours          0x0032   054   054   000    Old_age   Always       -       33859
 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       -       145
192 Power-Off_Retract_Count 0x0032   200   200   000    Old_age   Always       -       31
193 Load_Cycle_Count        0x0032   170   170   000    Old_age   Always       -       90973
194 Temperature_Celsius     0x0022   119   104   000    Old_age   Always       -       24
196 Reallocated_Event_Count 0x0032   001   001   000    Old_age   Always       -       819
197 Current_Pending_Sector  0x0032   198   198   000    Old_age   Always       -       326
198 Offline_Uncorrectable   0x0030   200   200   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      -       80

SMART Error Log Version: 1
ATA Error Count: 11 (device log contains only the most recent five errors)
    CR = Command Register [HEX]
    FR = Features Register [HEX]
    SC = Sector Count Register [HEX]
    SN = Sector Number Register [HEX]
    CL = Cylinder Low Register [HEX]
    CH = Cylinder High Register [HEX]
    DH = Device/Head Register [HEX]
    DC = Device Command Register [HEX]
    ER = Error register [HEX]
    ST = Status register [HEX]
Powered_Up_Time is measured from power on, and printed as
DDd+hh:mm:SS.sss where DD=days, hh=hours, mm=minutes,
SS=sec, and sss=millisec. It "wraps" after 49.710 days.

Error 11 occurred at disk power-on lifetime: 33842 hours (1410 days + 2 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 60 b0 a8 d7 e1  Error: UNC 96 sectors at LBA = 0x01d7a8b0 = 30910640

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  c8 00 60 a0 a8 d7 e1 08  17d+13:32:19.391  READ DMA
  ef 10 02 00 00 00 a0 08  17d+13:32:19.391  SET FEATURES [Enable SATA feature]
  ec 00 00 00 00 00 a0 08  17d+13:32:19.390  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 08  17d+13:32:19.390  SET FEATURES [Set transfer mode]

Error 10 occurred at disk power-on lifetime: 33842 hours (1410 days + 2 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 60 c8 a8 d7 e1  Error: UNC 96 sectors at LBA = 0x01d7a8c8 = 30910664

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  c8 00 60 a0 a8 d7 e1 08  17d+13:32:11.498  READ DMA
  ef 10 02 00 00 00 a0 08  17d+13:32:11.498  SET FEATURES [Enable SATA feature]
  ec 00 00 00 00 00 a0 08  17d+13:32:11.497  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 08  17d+13:32:11.497  SET FEATURES [Set transfer mode]

Error 9 occurred at disk power-on lifetime: 33842 hours (1410 days + 2 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 60 a8 a8 d7 e1  Error: UNC 96 sectors at LBA = 0x01d7a8a8 = 30910632

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  c8 00 60 a0 a8 d7 e1 08  17d+13:32:07.412  READ DMA
  c8 00 08 98 a8 d7 e1 08  17d+13:32:07.412  READ DMA

Error 8 occurred at disk power-on lifetime: 33841 hours (1410 days + 1 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 08 48 f9 80 e1  Error: UNC 8 sectors at LBA = 0x0180f948 = 25229640

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  c8 00 08 48 f9 80 e1 08  17d+13:12:31.938  READ DMA
  ef 10 02 00 00 00 a0 08  17d+13:12:31.938  SET FEATURES [Enable SATA feature]
  ec 00 00 00 00 00 a0 08  17d+13:12:31.937  IDENTIFY DEVICE
  ef 03 46 00 00 00 a0 08  17d+13:12:31.937  SET FEATURES [Set transfer mode]

Error 7 occurred at disk power-on lifetime: 33841 hours (1410 days + 1 hours)
  When the command that caused the error occurred, the device was active or idle.

  After command completion occurred, registers were:
  ER ST SC SN CL CH DH
  -- -- -- -- -- -- --
  40 51 08 48 f9 80 e1  Error: UNC 8 sectors at LBA = 0x0180f948 = 25229640

  Commands leading to the command that caused the error were:
  CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
  -- -- -- -- -- -- -- --  ----------------  --------------------
  c8 00 08 48 f9 80 e1 08  17d+13:12:29.429  READ DMA
  c8 00 b8 48 f5 80 e1 08  17d+13:12:29.410  READ DMA

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%     33858         384848
# 2  Short offline       Completed: read failure       80%     33857         1951525160

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.

EDIT

I cloned sda disk using:

ddrescue -d -f -r3 /dev/sda /dev/sde ddrescue.logfile

GNU ddrescue 1.19
Initial status (read from logfile)
rescued:     1000 GB,  errsize:    4096 B,  errors:       3

Current status
rescued:     1000 GB,  errsize:    4096 B,  current rate:        0 B/s
   ipos:     1052 kB,   errors:       3,    average rate:        0 B/s
   opos:     1052 kB, run time:    3.13 m,  successful read:    3.13 m ago

But the cloned disk sde says as well: mdadm: No md superblock detected on /dev/sde1. Could I recover those superblocks?

  • 2
    use ddrescue and pray! – Ipor Sircer Nov 11 '16 at 10:15
  • sda cloned only with 4096B not recovered, but what about superblock error? How could I fix it? – blacksoul Nov 11 '16 at 18:02
  • As I don't have experience with RAID recovery, I'd only like to comment, that the next time, you choose to create an array, do yourself a favor and with 4 disks, use either RAID10 or RAID6. – LinuxSecurityFreak Nov 13 '16 at 10:11
  • I couldn't... I need at least 3TB of the 4 – blacksoul Nov 13 '16 at 10:16
  • 1
    mdadm --assume-clean ..., and be careful! – Ipor Sircer Nov 14 '16 at 12:53
2
+100

We need to split your problem into two:

  1. Rebuild the array for missing /dev/sda superblock.
  2. Handle the damaged data on /dev/sdc

Rebuilding the array

I presume that the 4kB block not recovered from /dev/sda was the superblock, because your partition started at 1MiB (2048 sectors), and the superblock started at +8 sectors into the partition (2056 sectors), exactly on the 2056 sector mark where the bad sector exists. The assumption is that the REST of the data on that drive is 100% intact.

The problem with --assume-clean in general, is that you need to be extremely careful that the parameters exactly match what would have been used at the time the array was created. Changes in default values since your array creation date of Tue Aug 28 17:44:52 2012 are your ENEMY here. Metadata version, bitmap assumption (devices larger than 100GB get them automatically now), raid layout, etc.

If you're not absolutely certain, I would strongly suggest cloning ALL 4 of the drives to else (in an absolute pinch you could even use a single drive with 4 partitions each of 1TB/1953122952 sectors), and trying to re-assemble that instead. As /dev/sda is starting to fail as well as /dev/sdc, and you probably bought all your drives at the same time, maybe even two complete copies of the data, in case you have a further drive failure in trying to recover (depends on how valuable you consider your data).

If assume-clean works on the test copy, you're well-placed to move it elsewhere.

Here's some script help for you, distilling what you gave above (note that --examine reports in units of sectors for some values, but --create takes in units of KiB).

#!/bin/bash
# Facts we know about your array, from your mdadm -E output.
num_devices=4
num_spares=0
chunk_size=512 # KiB
data_offset=1024 # KiB
drive_size=976561152 # KiB
uuid=87fdc598:a995d0f7:41123bcf:e2760aeb
metadata_ver=1.2
name=itake:0
bitmap=none
original_device_order=(/dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1)
# I assume you recovered:
# /dev/sda to /dev/sde
# /dev/sdc to /dev/sdf
# If not, adjust as needed.
#
# Read all the way to the bottom of my response first, because you
# MIGHT want to use 'missing' in place of /dev/sdf1 initially.
new_device_order=(/dev/sde1 /dev/sdb1 /dev/sdf1 /dev/sdd1)

mdadm --create /dev/md0 \
--level 5 --layout left-symmetric
-n $num_devices -x $num_spares \
--uuid $uuid \
--metadata $metadata_ver \
--chunk $chunk_size
--size $drive_size \
--data-offset $data_offset \
--name $name \
--bitmap $bitmap \
${new_device_order[@]}  

Scrubbing the array (option 1)

We know /dev/sdc had bad sectors in the middle of your data area, and as a slightly more nuclear option, you could pass missing in place of /dev/sdf1 during the array creation, and then do mdadm --add /dev/md0 /dev/sdf1 to force a rebuild from the other devices onto /dev/sdf1.

Scrubbing the array (option 2)

Now we need to fix up the fact that parts of /dev/sdc are gone, and in their place on /dev/sdf, there are just zeroed blocks.

echo repair >/sys/devices/virtual/block/md0/md/sync_action

At the end of this, you should have it repaired, but I'm not 100% certain of the behavior that will be taken to recovery those blocks.

  • I like this solution you proposed. I can't clone the 4 disks but I already bought 2 for cloning sda and sdc. The first one, sda, is already cloned but sdc is in progress yet. I hope it will finish this weekend. The performance of sdc is bad, I guess because it's failing, so it's doing it slowly – blacksoul Nov 16 '16 at 15:08
  • I could "successfuly" recover the RAID with your solution, but now I can't mount the volume: paste.debian.net/900401 I forgot to say that I have a LVM volume on it, but lvscan does nothing now – blacksoul Dec 3 '16 at 17:42
  • I presume you mean that the RAID is a LVM physical volume. – robbat2 Dec 4 '16 at 16:42
  • Firstly I see you didn't pass in the new UUID, so I want to make sure you passed in all the other options. What scrub option did you use? Beyond that, does your LVM config scan all MDs? If it was an unpartitioned RAID, with just LVM PV on it, offset 0x200 (512) should have the text 'LABELONE'. I see a few options for what went wrong: - the old sda had a different partition offset (assumption stated above) - the re-assembly order was wrong - the superblock was in the lost portion of sda (but scrub should have fixed this) – robbat2 Dec 4 '16 at 16:49
  • 1
    For those following along at home, this was a successful data recovery in the end. The OP did mis-remember about LVM, as it was just a plain filesystem on the RAID instead. – robbat2 Feb 7 '17 at 3:55

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