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Storage Pool crashed (replacement disk inserted into the wrong slot)


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Hello,

I had the Synology DS1515+ (5 drive slots) and used to have one single Storage Pool consists of 4 drives (two 4TB drives and two 8TB drives, using SHR configuration), the extra slot on the machine was not in use. One day Drive #4 crashed and the Storage Pool went in Degraded state. I bought a new 16TB disk hoping to replace it and recover the Storage Pool.

 

But stupid me, I mistakenly took out the healthy Drive #3, replaced it with the new disk, and booted up the machine. I then clicked the Online Assemble option from the overview page in the Storage Manager app, but it had always failed to do so. After a few attempts and reboots, somehow I got to see a Repair option, I clicked it and it starts repairing the Storage Pool, with two originally healthy Drives #1 & #2, the mistakenly replaced 16TB Drive #3, and the originally crashed Drive #4. Up to this point, I had access to the data via the File Manager app, but the response was very slow.

 

After that, I moved the 16TB disk out from Drive #3 to Drive #5, and re-inserted the original 4TB healthy disk back into Drive #3. Now Drive #3 becomes Not Initialized (Healthy), and Drive #5 becomes Crashed (Healthy). I no longer have access to the storage via File Manager. But fortunately, the files seems to be accessible via the SSH terminal.

 

Any advice or guidance on my journey to recover the Storage Pool and the data would be gratefully received.

 

$ cat /proc/mdstat

Personalities : [raid1] [raid6] [raid5] [raid4] [raidF1]
md3 : active raid1 sdd6[0]
      3906998912 blocks super 1.2 [2/1] [U_]

md2 : active raid5 sda5[4] sde5[5] sdb5[7]
      11706562368 blocks super 1.2 level 5, 64k chunk, algorithm 2 [4/3] [UU_U]

md1 : active raid1 sda2[0] sdd2[2] sdb2[1]
      2097088 blocks [5/3] [UUU__]

md0 : active raid1 sdb1[0] sda1[3] sdd1[1]
      2490176 blocks [5/3] [UU_U_]

unused devices: <none>

 

$ vgdisplay --verbose

    Using volume group(s) on command line.
  --- Volume group ---
  VG Name               vg1000
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               14.54 TiB
  PE Size               4.00 MiB
  Total PE              3811904
  Alloc PE / Size       3811904 / 14.54 TiB
  Free  PE / Size       0 / 0
  VG UUID               1e1yFU-tU4H-iDgZ-biKn-nD1S-nK4V-P2lohD

  --- Logical volume ---
  LV Path                /dev/vg1000/lv
  LV Name                lv
  VG Name                vg1000
  LV UUID                AXdWh7-vAGX-2d7U-wXtb-quk3-LsHy-kPmdBx
  LV Write Access        read/write
  LV Creation host, time ,
  LV Status              available
  # open                 1
  LV Size                14.54 TiB
  Current LE             3811904
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     768
  Block device           253:0

  --- Physical volumes ---
  PV Name               /dev/md2
  PV UUID               hK1a7S-pdX1-5hjp-m53A-Tlpy-Jk9L-McEdHH
  PV Status             allocatable
  Total PE / Free PE    2858047 / 0

  PV Name               /dev/md3
  PV UUID               cJCeIW-KpCY-ez6a-JFk1-iRmT-djVM-Trec1B
  PV Status             allocatable
  Total PE / Free PE    953857 / 0

 

$ lvdisplay --verbose

    Using logical volume(s) on command line.
  --- Logical volume ---
  LV Path                /dev/vg1000/lv
  LV Name                lv
  VG Name                vg1000
  LV UUID                AXdWh7-vAGX-2d7U-wXtb-quk3-LsHy-kPmdBx
  LV Write Access        read/write
  LV Creation host, time ,
  LV Status              available
  # open                 1
  LV Size                14.54 TiB
  Current LE             3811904
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     768
  Block device           253:0

 

$ pvdisplay --verbose

    Using physical volume(s) on command line.
    Wiping cache of LVM-capable devices
  --- Physical volume ---
  PV Name               /dev/md2
  VG Name               vg1000
  PV Size               10.90 TiB / not usable 1.81 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              2858047
  Free PE               0
  Allocated PE          2858047
  PV UUID               hK1a7S-pdX1-5hjp-m53A-Tlpy-Jk9L-McEdHH

  --- Physical volume ---
  PV Name               /dev/md3
  VG Name               vg1000
  PV Size               3.64 TiB / not usable 640.00 KiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              953857
  Free PE               0
  Allocated PE          953857
  PV UUID               cJCeIW-KpCY-ez6a-JFk1-iRmT-djVM-Trec1B

 

$ df

Filesystem               1K-blocks        Used Available Use% Mounted on
/dev/md0                   2385528     1920488    346256  85% /
devtmpfs                   8208924           0   8208924   0% /dev
tmpfs                      8212972           4   8212968   1% /dev/shm
tmpfs                      8212972       15568   8197404   1% /run
tmpfs                      8212972           0   8212972   0% /sys/fs/cgroup
tmpfs                      8212972        1092   8211880   1% /tmp
/dev/mapper/cachedev_0 14989016436 14486635592 502380844  97% /volume1

 

$ mdadm --detail /dev/md0

/dev/md0:
        Version : 0.90
  Creation Time : Mon Nov 30 17:33:21 2015
     Raid Level : raid1
     Array Size : 2490176 (2.37 GiB 2.55 GB)
  Used Dev Size : 2490176 (2.37 GiB 2.55 GB)
   Raid Devices : 5
  Total Devices : 3
Preferred Minor : 0
    Persistence : Superblock is persistent

    Update Time : Sat Sep  2 14:02:50 2023
          State : active, degraded
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

           UUID : 7622664e:1657328c:3017a5a8:c86610be
         Events : 0.37057847

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       1       8       49        1      active sync   /dev/sdd1
       -       0        0        2      removed
       3       8        1        3      active sync   /dev/sda1
       -       0        0        4      removed

 

$ mdadm --detail /dev/md1

/dev/md1:
        Version : 0.90
  Creation Time : Sun Apr 28 18:35:40 2019
     Raid Level : raid1
     Array Size : 2097088 (2047.94 MiB 2147.42 MB)
  Used Dev Size : 2097088 (2047.94 MiB 2147.42 MB)
   Raid Devices : 5
  Total Devices : 3
Preferred Minor : 1
    Persistence : Superblock is persistent

    Update Time : Wed Jan  1 08:12:37 2014
          State : clean, degraded
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

           UUID : abcf619a:3398cc73:e7b2e964:f815f961 (local to host NAS)
         Events : 0.45611

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       8       18        1      active sync   /dev/sdb2
       2       8       50        2      active sync   /dev/sdd2
       -       0        0        3      removed
       -       0        0        4      removed

 

$ mdadm --detail /dev/md2

/dev/md2:
        Version : 1.2
  Creation Time : Mon Nov 30 18:19:21 2015
     Raid Level : raid5
     Array Size : 11706562368 (11164.25 GiB 11987.52 GB)
  Used Dev Size : 3902187456 (3721.42 GiB 3995.84 GB)
   Raid Devices : 4
  Total Devices : 3
    Persistence : Superblock is persistent

    Update Time : Sat Sep  2 13:32:07 2023
          State : clean, degraded
 Active Devices : 3
Working Devices : 3
 Failed Devices : 0
  Spare Devices : 0

         Layout : left-symmetric
     Chunk Size : 64K

           Name : NAS:2  (local to host NAS)
           UUID : 5ffcb2a1:80bc4d39:7f19eb5f:2d922605
         Events : 753119

    Number   Major   Minor   RaidDevice State
       4       8        5        0      active sync   /dev/sda5
       7       8       21        1      active sync   /dev/sdb5
       -       0        0        2      removed
       5       8       69        3      active sync   /dev/sde5

 

$ mdadm --detail /dev/md3

/dev/md3:
        Version : 1.2
  Creation Time : Mon Dec  3 12:19:09 2018
     Raid Level : raid1
     Array Size : 3906998912 (3726.00 GiB 4000.77 GB)
  Used Dev Size : 3906998912 (3726.00 GiB 4000.77 GB)
   Raid Devices : 2
  Total Devices : 1
    Persistence : Superblock is persistent

    Update Time : Sat Sep  2 14:03:35 2023
          State : clean, degraded
 Active Devices : 1
Working Devices : 1
 Failed Devices : 0
  Spare Devices : 0

           Name : NAS:3  (local to host NAS)
           UUID : adf75971:3ab713a6:ae03a0ce:ac3dc03d
         Events : 52290

    Number   Major   Minor   RaidDevice State
       0       8       54        0      active sync   /dev/sdd6
       -       0        0        1      removed

 

 

 

 

 

 

 

 

Screenshot 2023-09-02 at 18.44.19.png

Screenshot 2023-09-02 at 18.44.02.png

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  • 1 month later...

I've been struggling to restore the data for the past month. Here's the progress I made so far.

 

I tried to reboot the NAS. When it's restarted the Storage Manager UI showed an "Assemble Online" option. I clicked and waited, but after about 20 minutes, it failed and said "Cannot be assembled online". I thought it was the network problem, so I tried to reboot a few dozen times and made sure my Internet connection is OK. But the Storage Manager always showed the "Assemble Online" and always failed after I clicked it.

 

I tried to SSHed into the NAS and examine the folder structure. I found something interesting which might be helpful to restore the array and recover the data.

  1. The summary of MD and SD devices are shown in the images below.
    Screenshot2023-10-07at13_46_26.thumb.png.7b942433f088e0999bcafc8406384bb0.png
    Screenshot2023-10-07at13_46_11.thumb.png.5919d536ce157d764a319ae7f384b916.png
  2. I'm not sure what data fragments of md2 and md3 (these two MD drives that build up the entire Storage Pool) are on sde. But I think it should be the rebuild data to supplement the array of sda+sdb+[missing]+sdd, because it happens when I physically removed sdc and inserted sde and the Synology system tried to rebuild the Storage Pool using the array of sda+sdb+sde+sdd.
  3. I ran the command "sudo sfdisk -l" and it gives me this error "unrecognised disk label, get disk fail" for both md2 and md3. So I assume if I were able to fix both of these errors, I might have chance to recover the Storage Pool.

If you happen to have such experience in fixing the MD devices, would you please share it with me? Any advice and suggestions are appreciated. Thanks!

 

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