IO error montando raid

En este caso md3 se trata de un raid 1 que no es capaz de montar por errores en el segundo disco, lanzando los siguientes comandos observamos los siguientes errores:

# mount /dev/md3 /mnt/home/
mount: wrong fs type, bad option, bad superblock on /dev/md3,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

# smartctl -a /dev/sdb
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     0x000b   077   077   016    Pre-fail  Always       -       11928801
  2 Throughput_Performance  0x0005   139   139   054    Pre-fail  Offline      -       70
  3 Spin_Up_Time            0x0007   131   131   024    Pre-fail  Always       -       282 (Average 294)
  4 Start_Stop_Count        0x0012   100   100   000    Old_age   Always       -       22
  5 Reallocated_Sector_Ct   0x0033   001   001   005    Pre-fail  Always   FAILING_NOW 639
  7 Seek_Error_Rate         0x000b   099   099   067    Pre-fail  Always       -       1
  8 Seek_Time_Performance   0x0005   124   124   020    Pre-fail  Offline      -       33
  9 Power_On_Hours          0x0012   099   099   000    Old_age   Always       -       13406
 10 Spin_Retry_Count        0x0013   100   100   060    Pre-fail  Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       22
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       35
193 Load_Cycle_Count        0x0012   100   100   000    Old_age   Always       -       35
194 Temperature_Celsius     0x0002   187   187   000    Old_age   Always       -       32 (Min/Max 24/44)
196 Reallocated_Event_Count 0x0032   024   024   000    Old_age   Always       -       1528
197 Current_Pending_Sector  0x0022   001   001   000    Old_age   Always       -       11248
198 Offline_Uncorrectable   0x0008   100   100   000    Old_age   Offline      -       28
199 UDMA_CRC_Error_Count    0x000a   200   200   000    Old_age   Always       -       0

# dmesg
ata2.00: exception Emask 0x0 SAct 0x7fe0001f SErr 0x0 action 0x0
ata2.00: irq_stat 0x40000008
ata2.00: failed command: READ FPDMA QUEUED
ata2.00: cmd 60/08:a8:e8:0c:b7/00:00:9f:00:00/40 tag 21 ncq 4096 in
         res 51/40:08:e8:0c:b7/00:00:9f:00:00/40 Emask 0x409 (media error)
ata2.00: status: { DRDY ERR }
ata2.00: error: { UNC }
ata2.00: configured for UDMA/133
sd 1:0:0:0: [sdb] Unhandled sense code
sd 1:0:0:0: [sdb]  
Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
sd 1:0:0:0: [sdb]  
Sense Key : Medium Error [current] [descriptor]
Descriptor sense data with sense descriptors (in hex):
        72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00 
        9f b7 0c e8 
sd 1:0:0:0: [sdb]  
Add. Sense: Unrecovered read error - auto reallocate failed
sd 1:0:0:0: [sdb] CDB: 
Read(10): 28 00 9f b7 0c e8 00 00 08 00
end_request: I/O error, dev sdb, sector 2679573736
ata2: EH complete

El problema se debe a que está intentando escribir el journal que tenía pendiente, la solución es montarlo sin que lo escriba, perderemos los últimos datos pero posiblemente tengamos acceso a gran parte del disco.

# mount -o ro,noload /dev/md3 /mnt/home/