After my TS-431X failed to boot I tried two different repair centres. Both could not recover the hardware.
Decided to follow the guides to mount the array on an Ubuntu server. Most of the guides failed to assemble & mount the array. Eventually I found a procedure that works.
Ubuntu found the array but marked it as Inactive.
mdadm --stop /dev/md1
mdadm --assemble --force /dev/md1 /dev/sdb3 /dev/sdc3 /dev/sdd3 /dev/sde3
mdadm: /dev/md1 has been started with 3 drives (out of 4).
At this point drive-3 “/dev/sdd3” was missing, so I added it manually to the array:
mdadm --add /dev/md1 /dev/sdd3
Checked status with cat /proc/mdstat and it’s now rebuilding
Personalities : [raid1] [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid10]
md1 : active raid5 sdd3[4] sde3[3] sdc3[1] sdb3[0]
5830677504 blocks super 1.0 level 5, 512k chunk, algorithm 2 [4/3] [UU_U]
[>…] recovery = 0.0% (1527772/1943559168) finish=317.7min speed=101851K/sec
Check the Physical & Logical Volumes with pvdisplay and lvdisplay.
Then mounted the array Logical Volume & I can access my data (after the array rebuilds)
root@dl-160:~# ll /mnt/raid5/
total 164
drwxrwxrwx 34 root root 4096 Mar 22 01:30 ./
drwxr-xr-x 3 root root 4096 Aug 30 18:48 …/
drwxr-xr-x 3 root root 4096 Mar 22 01:27 .samba_python3/
d--------- 2 root root 4096 Mar 22 01:26 .swap/
drwxr-xr-x 13 root root 4096 May 9 02:00 .system/
drwxr-xr-x 3 root root 4096 Jul 10 11:18 .system_disk_data/
drwxrwxrwx 2 root root 4096 Jul 8 2023 .tmp/
drwxrwxrwx 3 root root 4096 Sep 21 2023 .wifi/
drwxrwxrwx 55 root root 4096 Feb 16 2025 Install/
drwxrwxrwx 10 root root 4096 Nov 28 2024 Media/
drwxrwxrwx 3 root root 4096 Jul 21 13:18 Public/
drwxrwxrwx 5 root root 4096 Jul 10 12:16 TimeMachine/
-rw------- 1 root root 9216 Jul 10 2023 aquota.user
drwxrwxrwx 5 root root 4096 Jul 7 2023 homes/
drwx------ 2 root root 16384 Jul 7 2023 lost+found/