Can't access to my shared files

I'm going to jump in with a little basic explanation.

A RAID 5 uses the capacity of one drive distributed across all drives for a CRC check.

For simplicity, think of it like a basic algebra equation across your 4 drives, where each number resides on a different drive.

1 + 2 + 3 = X

You can solve for X if you know what the other 3 values are, or if you already know what X is, you can solve for one of the other numbers, but if you are missing two of the values, the equation can not be solved.

You are missing 2 of the drives, so there is no way to solve the equation and rebuild the array. You are missing 1/3 of the data and the CRC value that can be used to rebuild the data.

Quote from Tamalou

That's what I don't understand.

How can I be missing 2 out of 4 disks when the tests you made me do show 3 disks going up on the RAID.

You are missing 2 because one is completely missing and the other one is missing the superblock. No superblock means no available raid signatures can be found to rebuild from.

You could try scanning the drives into images with something like ufs explorer to see if it can resurrect a raid from the images and recover data, but the chances are very slim with 2 drives inaccessible when only one is allowed to fail under normal circumstances. If you want to try it, be prepared for a long wait as data recovery is not fast.

I have used ufs explorer to recover data from broken raids before but there is no guarantee it will be able to given your situation.

I should also add that in order to rebuild a raid with its explorer, you need the professional version which is not cheap at $630 USD

Quote from Tamalou

I just thought of something else.

About a year ago I had replaced a failed disk, but I didn't do anything more RAID-wise, just physically replaced the disk.

Should I have passed command lines for RAID in relation to this change?

If you didn't add the new disk back to the array, you have likely been running degraded with no redundency ever since.