I don't want to approach this in a trial-and-error manner as I know this is the best thing to do if I want to loose my data.
I have a server with 4*2TB disks in RAID5 (yes I know it's not wise) on a Ubuntu 14.04.
Most of my data is in /home on RAID 5 and / is on RAID1.
I booted the server in rescue mode, but I can't figure out :
- if the problem is soft or hardware,
- if there's a way to remount the raid to recover these data.
I had a carefull read of Recovering a failed software RAID (raid.wiki.kernel.org), but as I'm not really confident about my diagnosis, I'd like to have some mindful judgement about what's going on and how to proceed if there's anything to do…
The only thins I tried was to mount my mds devices that weren't mounted, that worked for md2 mount /dev/md2 /mnt/, but I couldn't mount neither md0 nor md3 as I'm told /dev/md3: can't read superblock.
So far, this is what I checked :
EDIT parted -l
root@rescue:/mnt# parted -l
Model: ATA ST2000DM001-1CH1 (scsi)
Disk /dev/sda: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 20.5kB 1049kB 1029kB primary bios_grub
2 2097kB 10.5GB 10.5GB ext4 primary raid
3 10.5GB 2000GB 1989GB primary raid
4 2000GB 2000GB 536MB linux-swap(v1) primary
Model: ATA ST2000DM001-1CH1 (scsi)
Disk /dev/sdb: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 20.5kB 1049kB 1029kB primary bios_grub
2 2097kB 10.5GB 10.5GB ext4 primary raid
3 10.5GB 2000GB 1989GB primary raid
4 2000GB 2000GB 536MB linux-swap(v1) primary
Error: /dev/sdc: unrecognised disk label
Model: ATA ST2000DM001-1CH1 (scsi)
Disk /dev/sdc: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: unknown
Disk Flags:
Model: ATA ST2000DM001-1CH1 (scsi)
Disk /dev/sdd: 2000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:
Number Start End Size File system Name Flags
1 20.5kB 1049kB 1029kB primary bios_grub
2 2097kB 10.5GB 10.5GB ext4 primary raid
3 10.5GB 2000GB 1989GB primary raid
4 2000GB 2000GB 536MB linux-swap(v1) primary
Model: Linux Software RAID Array (md)
Disk /dev/md2: 10.5GB
Sector size (logical/physical): 512B/4096B
Partition Table: loop
Disk Flags:
Number Start End Size File system Flags
1 0.00B 10.5GB 10.5GB ext4
Error: /dev/md127: unrecognised disk label
Model: Linux Software RAID Array (md)
Disk /dev/md127: 10.5GB
Sector size (logical/physical): 512B/4096B
Partition Table: unknown
Disk Flags:
smartctl
root@rescue:~# smartctl -a -d ata /dev/sdc
smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.10.23-xxxx-std-ipv6-64-rescue] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net
Smartctl: Device Read Identity Failed: Input/output error
A mandatory SMART command failed: exiting. To continue, add one or more '-T permissive' options.
root@rescue:~# smartctl -a -d ata /dev/sdd
smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.10.23-xxxx-std-ipv6-64-rescue] (local build)
Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net
=== START OF INFORMATION SECTION ===
Model Family: Seagate Barracuda 7200.14 (AF)
Device Model: ST2000DM001-1CH164
Serial Number: W1E1KX59
LU WWN Device Id: 5 000c50 05c821593
Firmware Version: CC43
User Capacity: 2,000,398,934,016 bytes [2.00 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Device is: In smartctl database [for details use: -P show]
ATA Version is: 8
ATA Standard is: ATA-8-ACS revision 4
Local Time is: Tue Dec 30 16:04:49 2014 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: ( 584) seconds.
Offline data collection
capabilities: (0x73) SMART execute Offline immediate.
Auto Offline data collection on/off support.
Suspend Offline collection upon new
command.
No 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: ( 1) minutes.
Extended self-test routine
recommended polling time: ( 230) minutes.
Conveyance self-test routine
recommended polling time: ( 2) minutes.
SCT capabilities: (0x3085) SCT Status supported.
SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x000f 111 099 006 Pre-fail Always - 120551532
3 Spin_Up_Time 0x0003 095 095 000 Pre-fail Always - 0
4 Start_Stop_Count 0x0032 100 100 020 Old_age Always - 32
5 Reallocated_Sector_Ct 0x0033 097 097 036 Pre-fail Always - 4008
7 Seek_Error_Rate 0x000f 077 060 030 Pre-fail Always - 4351310995
9 Power_On_Hours 0x0032 079 079 000 Old_age Always - 18725
10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always - 0
12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always - 32
183 Runtime_Bad_Block 0x0032 100 100 000 Old_age Always - 0
184 End-to-End_Error 0x0032 100 100 099 Old_age Always - 0
187 Reported_Uncorrect 0x0032 089 089 000 Old_age Always - 11
188 Command_Timeout 0x0032 100 100 000 Old_age Always - 0 0 0
189 High_Fly_Writes 0x003a 100 100 000 Old_age Always - 0
190 Airflow_Temperature_Cel 0x0022 068 056 045 Old_age Always - 32 (Min/Max 26/35)
191 G-Sense_Error_Rate 0x0032 100 100 000 Old_age Always - 0
192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always - 31
193 Load_Cycle_Count 0x0032 100 100 000 Old_age Always - 46
194 Temperature_Celsius 0x0022 032 044 000 Old_age Always - 32 (0 16 0 0)
197 Current_Pending_Sector 0x0012 082 082 000 Old_age Always - 3056
198 Offline_Uncorrectable 0x0010 082 082 000 Old_age Offline - 3056
199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age Always - 0
240 Head_Flying_Hours 0x0000 100 253 000 Old_age Offline - 18708h+109m+27.415s
241 Total_LBAs_Written 0x0000 100 253 000 Old_age Offline - 24242600022
242 Total_LBAs_Read 0x0000 100 253 000 Old_age Offline - 112149279703
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: 18520 hours (771 days + 16 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 00 ff ff ff 0f Error: UNC at LBA = 0x0fffffff = 268435455
Commands leading to the command that caused the error were:
CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name
-- -- -- -- -- -- -- -- ---------------- --------------------
60 00 08 ff ff ff 4f 00 09:32:13.900 READ FPDMA QUEUED
ef 10 02 00 00 00 a0 00 09:32:13.898 SET FEATURES [Reserved for Serial ATA]
27 00 00 00 00 00 e0 00 09:32:13.898 READ NATIVE MAX ADDRESS EXT
ec 00 00 00 00 00 a0 00 09:32:13.898 IDENTIFY DEVICE
ef 03 46 00 00 00 a0 00 09:32:13.898 SET FEATURES [Set transfer mode]
Error 10 occurred at disk power-on lifetime: 18520 hours (771 days + 16 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 00 ff ff ff 0f Error: UNC at LBA = 0x0fffffff = 268435455
Commands leading to the command that caused the error were:
CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name
-- -- -- -- -- -- -- -- ---------------- --------------------
60 00 08 ff ff ff 4f 00 09:32:10.764 READ FPDMA QUEUED
60 00 08 ff ff ff 4f 00 09:32:10.763 READ FPDMA QUEUED
60 00 38 ff ff ff 4f 00 09:32:10.763 READ FPDMA QUEUED
ef 10 02 00 00 00 a0 00 09:32:10.763 SET FEATURES [Reserved for Serial ATA]
27 00 00 00 00 00 e0 00 09:32:10.763 READ NATIVE MAX ADDRESS EXT
Error 9 occurred at disk power-on lifetime: 18520 hours (771 days + 16 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 00 ff ff ff 0f Error: UNC at LBA = 0x0fffffff = 268435455
Commands leading to the command that caused the error were:
CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name
-- -- -- -- -- -- -- -- ---------------- --------------------
60 00 38 ff ff ff 4f 00 09:32:09.084 READ FPDMA QUEUED
61 00 08 00 88 38 41 00 09:32:07.445 WRITE FPDMA QUEUED
60 00 08 ff ff ff 4f 00 09:32:07.416 READ FPDMA QUEUED
60 00 08 ff ff ff 4f 00 09:32:07.416 READ FPDMA QUEUED
60 00 08 ff ff ff 4f 00 09:32:07.416 READ FPDMA QUEUED
Error 8 occurred at disk power-on lifetime: 18520 hours (771 days + 16 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 00 ff ff ff 0f Error: WP at LBA = 0x0fffffff = 268435455
Commands leading to the command that caused the error were:
CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name
-- -- -- -- -- -- -- -- ---------------- --------------------
61 00 40 ff ff ff 4f 00 09:32:04.118 WRITE FPDMA QUEUED
61 00 08 70 88 38 41 00 09:32:04.117 WRITE FPDMA QUEUED
61 00 40 ff ff ff 4f 00 09:32:04.117 WRITE FPDMA QUEUED
60 00 40 ff ff ff 4f 00 09:32:04.117 READ FPDMA QUEUED
60 00 08 ff ff ff 4f 00 09:32:04.117 READ FPDMA QUEUED
Error 7 occurred at disk power-on lifetime: 17319 hours (721 days + 15 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 00 50 a9 59 02 Error: UNC at LBA = 0x0259a950 = 39430480
Commands leading to the command that caused the error were:
CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name
-- -- -- -- -- -- -- -- ---------------- --------------------
60 00 00 00 aa 59 42 00 01:31:02.054 READ FPDMA QUEUED
60 00 00 00 a6 59 42 00 01:31:02.054 READ FPDMA QUEUED
60 00 00 00 92 36 42 00 01:30:55.032 READ FPDMA QUEUED
60 00 00 00 86 36 42 00 01:30:51.600 READ FPDMA QUEUED
60 00 00 00 82 36 42 00 01:30:51.593 READ FPDMA QUEUED
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% 18706 3848494344
# 2 Short offline Completed without error 00% 3481 -
# 3 Short offline Completed without error 00% 3472 -
# 4 Short offline Completed without error 00% 3472 -
# 5 Short offline Completed without error 00% 13 -
# 6 Short offline Completed without error 00% 5 -
# 7 Short offline Completed without error 00% 5 -
# 8 Short offline Completed without error 00% 0 -
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.
ls /dev
ls /dev
MAKEDEV md0 ptya0 ptyc5 ptyea ptyqf ptyt4 ptyv9 ptyxe ram11 sg1 tty34 ttyS1 ttyc2 ttye7 ttyqc ttyt1 ttyv6 ttyxb urandom
aer_inject md127 ptya1 ptyc6 ptyeb ptyr0 ptyt5 ptyva ptyxf ram12 sg2 tty35 ttyS2 ttyc3 ttye8 ttyqd ttyt2 ttyv7 ttyxc vcs
autofs md2 ptya2 ptyc7 ptyec ptyr1 ptyt6 ptyvb ptyy0 ram13 sg3 tty36 ttyS3 ttyc4 ttye9 ttyqe ttyt3 ttyv8 ttyxd vcs1
block md3 ptya3 ptyc8 ptyed ptyr2 ptyt7 ptyvc ptyy1 ram14 shm tty37 ttya0 ttyc5 ttyea ttyqf ttyt4 ttyv9 ttyxe vcs2
[…]
cat /proc/mdstat
cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] [faulty]
md127 : active raid1 sdc2[2]
10238912 blocks [4/1] [__U_]
md2 : active raid1 sdd2[3] sda2[0] sdb2[1]
10238912 blocks [4/3] [UU_U]
mdadm –detail
root@rescue:~# mdadm --detail /dev/md2
/dev/md2:
Version : 0.90
Creation Time : Tue Sep 2 16:46:34 2014
Raid Level : raid1
Array Size : 10238912 (9.76 GiB 10.48 GB)
Used Dev Size : 10238912 (9.76 GiB 10.48 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 2
Persistence : Superblock is persistent
Update Time : Sat Dec 27 17:31:03 2014
State : clean, degraded
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
UUID : 5a33c710:006f668d:a4d2adc2:26fd5302 (local to host rescue.ovh.net)
Events : 0.503145
Number Major Minor RaidDevice State
0 8 2 0 active sync /dev/sda2
1 8 18 1 active sync /dev/sdb2
2 0 0 2 removed
3 8 50 3 active sync /dev/sdd2
root@rescue:~# mdadm --detail /dev/md127
/dev/md127:
Version : 0.90
Creation Time : Tue Sep 2 16:46:34 2014
Raid Level : raid1
Array Size : 10238912 (9.76 GiB 10.48 GB)
Used Dev Size : 10238912 (9.76 GiB 10.48 GB)
Raid Devices : 4
Total Devices : 1
Preferred Minor : 127
Persistence : Superblock is persistent
Update Time : Sat Dec 27 17:31:16 2014
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Number Major Minor RaidDevice State
0 0 0 0 removed
1 0 0 1 removed
2 8 34 2 active sync /dev/sdc2
3 0 0 3 removed
And at last mdadm –examine sd*
root@rescue:~# mdadm --examine /dev/sd*
/dev/sda:
MBR Magic : aa55
Partition[0] : 3907029167 sectors at 1 (type ee)
mdadm: No md superblock detected on /dev/sda1.
/dev/sda2:
Magic : a92b4efc
Version : 0.90.00
UUID : 5a33c710:006f668d:a4d2adc2:26fd5302 (local to host rescue.ovh.net)
Creation Time : Tue Sep 2 16:46:34 2014
Raid Level : raid1
Used Dev Size : 10238912 (9.76 GiB 10.48 GB)
Array Size : 10238912 (9.76 GiB 10.48 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 2
Update Time : Sat Dec 27 18:20:56 2014
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Checksum : 78eed7b8 - correct
Events : 503147
Number Major Minor RaidDevice State
this 0 8 2 0 active sync /dev/sda2
0 0 8 2 0 active sync /dev/sda2
1 1 8 18 1 active sync /dev/sdb2
2 2 0 0 2 faulty removed
3 3 8 50 3 active sync /dev/sdd2
/dev/sda3:
Magic : a92b4efc
Version : 0.90.00
UUID : 4a417350:7192f812:a4d2adc2:26fd5302 (local to host rescue.ovh.net)
Creation Time : Tue Sep 2 16:46:35 2014
Raid Level : raid5
Used Dev Size : 1942745600 (1852.75 GiB 1989.37 GB)
Array Size : 5828236800 (5558.24 GiB 5968.11 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 3
Update Time : Mon Dec 22 10:33:05 2014
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 2
Spare Devices : 0
Checksum : 4d44c428 - correct
Events : 109608
Layout : left-symmetric
Chunk Size : 512K
Number Major Minor RaidDevice State
this 0 8 3 0 active sync /dev/sda3
0 0 8 3 0 active sync /dev/sda3
1 1 8 19 1 active sync /dev/sdb3
2 2 0 0 2 faulty removed
3 3 0 0 3 faulty removed
mdadm: No md superblock detected on /dev/sda4.
/dev/sdb:
MBR Magic : aa55
Partition[0] : 3907029167 sectors at 1 (type ee)
mdadm: No md superblock detected on /dev/sdb1.
/dev/sdb2:
Magic : a92b4efc
Version : 0.90.00
UUID : 5a33c710:006f668d:a4d2adc2:26fd5302 (local to host rescue.ovh.net)
Creation Time : Tue Sep 2 16:46:34 2014
Raid Level : raid1
Used Dev Size : 10238912 (9.76 GiB 10.48 GB)
Array Size : 10238912 (9.76 GiB 10.48 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 2
Update Time : Sat Dec 27 18:20:56 2014
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Checksum : 78eed7ca - correct
Events : 503147
Number Major Minor RaidDevice State
this 1 8 18 1 active sync /dev/sdb2
0 0 8 2 0 active sync /dev/sda2
1 1 8 18 1 active sync /dev/sdb2
2 2 0 0 2 faulty removed
3 3 8 50 3 active sync /dev/sdd2
/dev/sdb3:
Magic : a92b4efc
Version : 0.90.00
UUID : 4a417350:7192f812:a4d2adc2:26fd5302 (local to host rescue.ovh.net)
Creation Time : Tue Sep 2 16:46:35 2014
Raid Level : raid5
Used Dev Size : 1942745600 (1852.75 GiB 1989.37 GB)
Array Size : 5828236800 (5558.24 GiB 5968.11 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 3
Update Time : Mon Dec 22 10:33:05 2014
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 2
Spare Devices : 0
Checksum : 4d44c43a - correct
Events : 109608
Layout : left-symmetric
Chunk Size : 512K
Number Major Minor RaidDevice State
this 1 8 19 1 active sync /dev/sdb3
0 0 8 3 0 active sync /dev/sda3
1 1 8 19 1 active sync /dev/sdb3
2 2 0 0 2 faulty removed
3 3 0 0 3 faulty removed
mdadm: No md superblock detected on /dev/sdb4.
mdadm: No md superblock detected on /dev/sdc.
mdadm: No md superblock detected on /dev/sdc1.
mdadm: No md superblock detected on /dev/sdc2.
mdadm: No md superblock detected on /dev/sdc3.
mdadm: No md superblock detected on /dev/sdc4.
/dev/sdd:
MBR Magic : aa55
Partition[0] : 3907029167 sectors at 1 (type ee)
mdadm: No md superblock detected on /dev/sdd1.
/dev/sdd2:
Magic : a92b4efc
Version : 0.90.00
UUID : 5a33c710:006f668d:a4d2adc2:26fd5302 (local to host rescue.ovh.net)
Creation Time : Tue Sep 2 16:46:34 2014
Raid Level : raid1
Used Dev Size : 10238912 (9.76 GiB 10.48 GB)
Array Size : 10238912 (9.76 GiB 10.48 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 2
Update Time : Sat Dec 27 18:20:56 2014
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Checksum : 78eed7ee - correct
Events : 503147
Number Major Minor RaidDevice State
this 3 8 50 3 active sync /dev/sdd2
0 0 8 2 0 active sync /dev/sda2
1 1 8 18 1 active sync /dev/sdb2
2 2 0 0 2 faulty removed
3 3 8 50 3 active sync /dev/sdd2
/dev/sdd3:
Magic : a92b4efc
Version : 0.90.00
UUID : 4a417350:7192f812:a4d2adc2:26fd5302 (local to host rescue.ovh.net)
Creation Time : Tue Sep 2 16:46:35 2014
Raid Level : raid5
Used Dev Size : 1942745600 (1852.75 GiB 1989.37 GB)
Array Size : 5828236800 (5558.24 GiB 5968.11 GB)
Raid Devices : 4
Total Devices : 3
Preferred Minor : 3
Update Time : Mon Dec 22 01:55:55 2014
State : active
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Checksum : 4d429eeb - correct
Events : 109599
Layout : left-symmetric
Chunk Size : 512K
Number Major Minor RaidDevice State
this 3 8 51 3 active sync /dev/sdd3
0 0 8 3 0 active sync /dev/sda3
1 1 8 19 1 active sync /dev/sdb3
2 2 0 0 2 faulty removed
3 3 8 51 3 active sync /dev/sdd3
mdadm: No md superblock detected on /dev/sdd4.
EDIT
In a last attempt, I unmounted /dev/md2 and stopped it with mdadm.
Then I was able to assemble /dev/md3:
mdadm --assemble --force /dev/md3 /dev/sd[abd]3
mdadm: forcing event count in /dev/sdd3(3) from 109599 upto 109608
mdadm: clearing FAULTY flag for device 2 in /dev/md3 for /dev/sdd3
mdadm: Marking array /dev/md3 as 'clean'
mdadm: /dev/md3 has been started with 3 drives (out of 4).
Syslog at the time:
md/raid:md3: device sda3 operational as raid disk 0
md/raid:md3: device sdd3 operational as raid disk 3
md/raid:md3: device sdb3 operational as raid disk 1
md/raid:md3: allocated 4338kB
md/raid:md3: raid level 5 active with 3 out of 4 devices, algorithm 2
RAID conf printout:
--- level:5 rd:4 wd:3
disk 0, o:1, dev:sda3
disk 1, o:1, dev:sdb3
disk 3, o:1, dev:sdd3
md3: detected capacity change from 0 to 5968114483200
md3: unknown partition table
And the RAID seemed OK:
root@rescue:/mnt# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] [faulty]
md3 : active raid5 sda3[0] sdd3[3] sdb3[1]
5828236800 blocks level 5, 512k chunk, algorithm 2 [4/3] [UU_U]
[…]
But I couldn't mount it:
root@rescue:/mnt# 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
While doing that, many errors appeared in the syslog:
ata4.00: exception Emask 0x0 SAct 0xfe SErr 0x0 action 0x0
ata4.00: irq_stat 0x40000008
ata4.00: failed command: READ FPDMA QUEUED
ata4.00: cmd 60/18:08:18:34:63/00:00:e5:00:00/40 tag 1 ncq 12288 in
res 41/40:18:18:34:63/00:00:e5:00:00/00 Emask 0x409 (media error) <F>
ata4.00: status: { DRDY ERR }
ata4.00: error: { UNC }
ata4.00: configured for UDMA/133
sd 3:0:0:0: [sdd] Unhandled sense code
sd 3:0:0:0: [sdd]
Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
sd 3:0:0:0: [sdd]
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
e5 63 34 18
sd 3:0:0:0: [sdd]
Add. Sense: Unrecovered read error - auto reallocate failed
sd 3:0:0:0: [sdd] CDB:
Read(10): 28 00 e5 63 34 18 00 00 18 00
blk_update_request: 46 callbacks suppressed
end_request: I/O error, dev sdd, sector 3848483864
md/raid:md3: read error not correctable (sector 3828001816 on sdd3).
md/raid:md3: Disk failure on sdd3, disabling device.
I tried to correct them with hdparmbut there are too many of them and each time a bunch of new one appears.
Obviously, as mentionned in the syslog md/raid:md3: Disk failure on sdd3, disabling device. at the same time I tried to mount md3, the array's state changed to FAILED.
It seems that I have lost this battle…
Best Answer
If I understand things right your /dev/md3 is raid5 and should consist of /dev/sda3, /dev/sdb3, /dev/sdc3 (which no longer exist) and /dev/sdd3.
So what do you get from mdadm --detail /dev/md3?
Why does /dev/sdc still seem to have a broken partition table?
Maybe it would be possible to restore your data even though the partitions from /dev/sdc are still missing, but I would try the following rescue operation:
1) Use some live CD to boot, do not mount any partitions or raid disks.
2) Make raw image copies of all disks, yes you will need more than 8 TB of free space somewhere, maybe on some network drive. If your disks are physically OK you can use dd to make the copies. If some disk is physically broken, you might have to use some ddrescue program instead.
3) Make working raw image copies of the original raw image copies, yes you will need another 8 TB of free space for that.
4) Use a virtual machine like qemu or virtualbox. Start by booting the virtual machine with some good live CD suitable for data rescue. Systemrescuecd might be a good choice.
5) From within the virtual machine, using your working raw disk image copies, try to fix your working raw disk image copies. One place to start might be to add a partition table to the working raw disk image copy of /dev/sdc. The partition table of /dev/sdc should probably look the same as the partition table of /dev/sdd.
6) When you think that you have fixed the problem, boot your virtual machine from your working disk image copies.
7) Once your virtual machine has proven that your disk image files have been fixed, copy the fixed images back to your physical disks. If some physical disk is broken you might want to replace it first.
If you at some stage find that your attempts to fix the broken raid only have made things worse, overwrite your working raw disk images with the original raw disk images and restart.