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I have a Raid 5 with 4 disk and is not working, I can't detect what disk is failing for replacement Could you help me? Thanks in advance

Here is some information

root@debian:~# mount /dev/md0 /mnt/
mount: /dev/md0: can't read superblock




root@debian:~# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid1] [raid10]
md0 : inactive sda2[0](S) sdc2[2](S) sdb2[1](S) sdd2[3](S)
      15558811648 blocks super 1.2

md1 : active (auto-read-only) raid5 sdc3[2] sdb3[1] sdd3[3] sda3[0]
      49950720 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/4] [UUUU]

unused devices: <none>





root@debian:~# mdadm -E /dev/sd[a-d]2
/dev/sda2:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 28325057:d60d1808:d0f8b823:c32eb0e7
           Name : 8aServer:0
  Creation Time : Fri Sep 18 16:06:57 2015
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 7779405824 (3709.51 GiB 3983.06 GB)
     Array Size : 11669108736 (11128.53 GiB 11949.17 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262064 sectors, after=0 sectors
          State : clean
    Device UUID : 0d668096:d7c99df1:54709144:27fc4ff7

Internal Bitmap : 8 sectors from superblock
    Update Time : Thu Dec 24 10:59:49 2020
       Checksum : 4ea4321 - correct
         Events : 3213934

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 0
   Array State : A.A. ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdb2:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 28325057:d60d1808:d0f8b823:c32eb0e7
           Name : 8aServer:0
  Creation Time : Fri Sep 18 16:06:57 2015
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 7779405824 (3709.51 GiB 3983.06 GB)
     Array Size : 11669108736 (11128.53 GiB 11949.17 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262056 sectors, after=0 sectors
          State : active
    Device UUID : d5db5aba:78587f78:09b296fe:fc945872

Internal Bitmap : 8 sectors from superblock
    Update Time : Sun Jul  5 06:51:16 2020
  Bad Block Log : 512 entries available at offset 72 sectors
       Checksum : e3d3687b - correct
         Events : 1659832

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 1
   Array State : AAAA ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdc2:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 28325057:d60d1808:d0f8b823:c32eb0e7
           Name : 8aServer:0
  Creation Time : Fri Sep 18 16:06:57 2015
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 7779405824 (3709.51 GiB 3983.06 GB)
     Array Size : 11669108736 (11128.53 GiB 11949.17 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262064 sectors, after=0 sectors
          State : clean
    Device UUID : 9a5afde5:0036d08e:87eb6c78:a9e9c305

Internal Bitmap : 8 sectors from superblock
    Update Time : Thu Dec 24 10:59:49 2020
       Checksum : 33e90afd - correct
         Events : 3213934

         Layout : left-symmetric
     Chunk Size : 512K

   Device Role : Active device 2
   Array State : A.A. ('A' == active, '.' == missing, 'R' == replacing)
/dev/sdd2:
          Magic : a92b4efc
        Version : 1.2
    Feature Map : 0x1
     Array UUID : 28325057:d60d1808:d0f8b823:c32eb0e7
           Name : 8aServer:0
  Creation Time : Fri Sep 18 16:06:57 2015
     Raid Level : raid5
   Raid Devices : 4

 Avail Dev Size : 7779405824 (3709.51 GiB 3983.06 GB)
     Array Size : 11669108736 (11128.53 GiB 11949.17 GB)
    Data Offset : 262144 sectors
   Super Offset : 8 sectors
   Unused Space : before=262064 sectors, after=0 sectors
          State : active
    Device UUID : 8fb94746:069f6199:d849383b:60f4eef5

Internal Bitmap : 8 sectors from superblock
    Update Time : Wed Dec 23 19:38:11 2020
       Checksum : 51bf6683 - correct
         Events : 3213899

         Layout : left-symmetric
     Chunk Size : 512K

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





root@debian:~# e2fsck /dev/md0
e2fsck 1.43.4 (31-Jan-2017)
e2fsck: Invalid argument while trying to open /dev/md0

The superblock could not be read or does not describe a valid ext2/ext3/ext4
filesystem.  If the device is valid and it really contains an ext2/ext3/ext4
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>
 or
    e2fsck -b 32768 <device>
Daniel Segovia
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    You'd be shocked how many people still using R5 with big disks come here every month saying 'help me recover my data' when the warnings about using R5 with big disks is well over a decade old. Just restore your last backup to something that's viable - R1/10 and R6/60 (plus raidz if you like it) are the only games in town. – Chopper3 Dec 26 '20 at 15:41
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    Does running `mdadm --run /dev/md0` *before* mounting change anything? If not, please show the output of `mdadm -D /dev/md0` – shodanshok Dec 26 '20 at 23:11

1 Answers1

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I had two broken disk, I saw in logs with "Update Time" key, one of then died in June and the another Dec 23

I repaired the disk and I could get the information.

Daniel Segovia
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