4 hours ago, chropass said:

there's no lost+found folder.

The physical disk was not repaired, and apparently doesn't need repair, so there is no lost+found.

4 hours ago, chropass said:

looks like some files/directories are missing

Any files written to emulated disk1 (after the disk was disabled) are not on the physical disk.

Can you identify which files/directories are missing from the Unassigned Device? Can you see them on the repaired emulated disk1?

29 minutes ago, trurl said:

The physical disk was not repaired, and apparently doesn't need repair, so there is no lost+found.

Any files written to emulated disk1 (after the disk was disabled) are not on the physical disk.

Can you identify which files/directories are missing from the Unassigned Device? Can you see them on the repaired emulated disk1?

I'm trying to identify them, but I feel like I cannot fully check every file...

Now I'm starting to think I should just compare the whole 4TB worth of subdirectories between the emulated disk1 and the physical disk and see what's not there.

Maybe it'll take several hours?

I've been identifying what files should I salvage from the physical HDD before rebuilding it.

And after finishing it, I finally decided to start rebuild.

Before doing that, I assume the loosen cable caused the issue, I wanted to make sure that the sata cables are properly connected. So i shutdown the server.

After checking it, I booted the server, and now, somehow the server won't start up.
I didn't force shutdown this time. Just initiated it from WebGUI.

Trouble after trouble...

But as for the initial issue, I think now I know what I should next. Assign the disk again and start the array. the disk would be rebuilt automatically, I think.
Since the initial issue is almost solved, I set this post as solved now.

Thank you everyone patiently helped me for more than a week. I really appriciate you!

Edited May 24May 24 by chropass