[27969.398749] sd 5:0:0:0: [sdb] 3907029168 512-byte hardware sectors (2000399 MB)
[27969.398749] sd 5:0:0:0: [sdb] Write Protect is off
[27969.398749] sd 5:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[27969.398749] sd 5:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[27972.117543] ata6.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x0
[27972.117543] ata6.00: irq_stat 0x48000000
[27972.117543] ata6.00: cmd 60/08:00:ff:71:79/00:00:07:00:00/40 tag 0 ncq 4096 in
[27972.117543]          res 41/40:00:00:72:79/24:00:07:00:00/40 Emask 0x409 (media error) <F>
[27972.117543] ata6.00: status: { DRDY ERR }
[27972.117543] ata6.00: error: { UNC }
[27972.126765] ata6.00: configured for UDMA/133
[27972.126765] ata6: EH complete
[27972.126765] sd 5:0:0:0: [sdb] 3907029168 512-byte hardware sectors (2000399 MB)
[27972.126765] sd 5:0:0:0: [sdb] Write Protect is off
[27972.126765] sd 5:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[27972.126765] sd 5:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[27975.172076] ata6.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x0
[27975.172076] ata6.00: irq_stat 0x48000000
[27975.172076] ata6.00: cmd 60/08:00:ff:71:79/00:00:07:00:00/40 tag 0 ncq 4096 in
[27975.172076]          res 41/40:00:00:72:79/24:00:07:00:00/40 Emask 0x409 (media error) <F>
[27975.172076] ata6.00: status: { DRDY ERR }
[27975.172076] ata6.00: error: { UNC }
[27975.181327] ata6.00: configured for UDMA/133
[27975.181327] ata6: EH complete
[27975.186757] sd 5:0:0:0: [sdb] 3907029168 512-byte hardware sectors (2000399 MB)
[27975.186757] sd 5:0:0:0: [sdb] Write Protect is off
[27975.186757] sd 5:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[27975.186757] sd 5:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[27977.659491] ata6.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x0
[27977.659491] ata6.00: irq_stat 0x48000000
[27977.659491] ata6.00: cmd 60/08:00:ff:71:79/00:00:07:00:00/40 tag 0 ncq 4096 in
[27977.659491]          res 41/40:00:00:72:79/24:00:07:00:00/40 Emask 0x409 (media error) <F>
[27977.659491] ata6.00: status: { DRDY ERR }
[27977.659491] ata6.00: error: { UNC }
[27977.852642] ata6.00: configured for UDMA/133
[27977.852642] ata6: EH complete
[27977.854748] sd 5:0:0:0: [sdb] 3907029168 512-byte hardware sectors (2000399 MB)
[27977.854748] sd 5:0:0:0: [sdb] Write Protect is off
[27977.854748] sd 5:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[27977.854748] sd 5:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[27980.573764] ata6.00: exception Emask 0x0 SAct 0x1 SErr 0x0 action 0x0
[27980.573764] ata6.00: irq_stat 0x48000000
[27980.573764] ata6.00: cmd 60/08:00:ff:71:79/00:00:07:00:00/40 tag 0 ncq 4096 in
[27980.573764]          res 41/40:00:00:72:79/24:00:07:00:00/40 Emask 0x409 (media error) <F>
[27980.573764] ata6.00: status: { DRDY ERR }
[27980.573764] ata6.00: error: { UNC }
[27980.583204] ata6.00: configured for UDMA/133
[27980.583204] sd 5:0:0:0: [sdb] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE,SUGGEST_OK
[27980.583204] sd 5:0:0:0: [sdb] Sense Key : Medium Error [current] [descriptor]
[27980.583204] Descriptor sense data with sense descriptors (in hex):
[27980.583204]         72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00
[27980.583204]         07 79 72 00
[27980.583204] sd 5:0:0:0: [sdb] Add. Sense: Unrecovered read error - auto reallocate failed
[27980.583204] end_request: I/O error, dev sdb, sector 125399552
[27980.583204] ata6: EH complete
[27980.583204] raid1: sdb: unrecoverable I/O read error for block 125399424
[27980.583204] sd 5:0:0:0: [sdb] 3907029168 512-byte hardware sectors (2000399 MB)
[27980.583204] sd 5:0:0:0: [sdb] Write Protect is off
[27980.583204] sd 5:0:0:0: [sdb] Mode Sense: 00 3a 00 00
[27980.583204] sd 5:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
[27981.086035] md: md0: recovery done.

md0 : active raid1 sda1[2] sdb1[0]
      488287488 blocks [2/1] [U_]
      [==>..................]  recovery = 12.8% (62687872/488287488) finish=269546.4min speed=24K/sec
     
unused devices: <none>
# mdadm --fail /dev/sdb1
mdadm: /dev/sdb1 does not appear to be an md device
# mdadm --fail /dev/sdb1
# mdadm --manage /dev/md0 --fail /dev/sdb1
mdadm --manage /dev/md0 --fail /dev/sdb1
mdadm: set /dev/sdb1 faulty in /dev/md0