Sometimes repair can't figure out names of files or folders, or which folders a file belongs in. Those are put in lost+found.

22 hours ago, dthedj said:

I therefore have a backup of both disks.

If you are happy with your backups, restoring both disks from backup might be the simplest solution.

To confirm the recovery process: if I restore from a backup, do I simply reassign Disk 9 and restart the array?

Will both disks then appear as empty, implying that without a backup, this data would be permanently lost?

This experience is concerning, especially for a system designed for data redundancy.

What are the potential root causes for this—could it be hardware-related?

What should I do to ensure this doesn't happen again?"

Thanks

Just to make sure we have the current state of things

Attach Diagnostics ZIP to your NEXT post in this thread.

Here's the latest diagnostics

unraid-diagnostics-20260407-1114.zip

Since only disk9 is missing, no other drives are disabled or invalid, and you have single parity, you should be able to start the array in normal mode. Do that and post new diagnostics.

I restarted the array with disk 9 but it went back to same issue with both disk 6 and 9 showing empty and disk 9 emulated.

unraid-diagnostics-20260407-1449.zip

Didn't really expect a change. Just wanted to have the latest info to reference.

To get the array back in sync, you can rebuild disk9, which would result in an empty disk. Then restore disk9 from backup.

Or you can use that disk you repaired outside the array and New Config it back into the array as disk9, and rebuild parity instead. If you use the repaired disk, it will have some lost+found as you have seen, that would probably have to be restored from backup.

Either way you will have to restore disk6 from backup.

3 hours ago, dthedj said:

What should I do to ensure this doesn't happen again?

If you are ever in doubt about what to do, ask on the forum with your diagnostics before doing anything.

Disturbing connections are a very common reason for problems when replacing disks.

Before rebuilding any disk, make sure all disks are shown as mountable. If you rebuild an unmountable disk, the result will be an unmountable disk. If any disk is unmountable, check filesystem to repair it before proceeding with rebuild.

During rebuild, you should see writing to the rebuilding disk, reading from all other disks, and zero in the ERRORS column for all disks. If there are errors, the rebuild may not be accurate, which could result in unmountable. Hopefully, the reason for the errors will just be connection problems, and you can shutdown, fix them, and start the rebuild again.

Make sure all array disks are healthy. Each disk in the parity array is an independent filesystem that can be read all by itself in any Linux. But, it must reliably read every bit of all disks to reliably rebuild every bit of a disabled/missing disk.

Unraid monitors certain SMART attributes and will warn you for those. For each of your WD disks click on it to get to its page and add attributes 1, 200 for monitoring.

Do any disks show SMART (👎) warning on the DASHBOARD page?

Setup Notifications to alert you immediately by email or other agent as soon as a problem is detected.

48 minutes ago, trurl said:

Didn't really expect a change. Just wanted to have the latest info to reference.

To get the array back in sync, you can rebuild disk9, which would result in an empty disk. Then restore disk9 from backup.

For this method, I stop the array and restart without disk 9. Then, stop again and restart with disk 9?

Or you can use that disk you repaired outside the array and New Config it back into the array as disk9, and rebuild parity instead. If you use the repaired disk, it will have some lost+found as you have seen, that would probably have to be restored from backup.

Please let know how to proceed for this method.

Either way you will have to restore disk6 from backup.

Which method is less "stressful" on the disks? Which one you recommend?

Thanks

35 minutes ago, trurl said:

Unraid monitors certain SMART attributes and will warn you for those. For each of your WD disks click on it to get to its page and add attributes 1, 200 for monitoring.

So for each of my drives, I need to add "1, 200" in SMART Attribute Notifications and click APPLY?

38 minutes ago, trurl said:

Do any disks show SMART (👎) warning on the DASHBOARD page?

Yes, three disks are showing errors. What should I do about this?

5 hours ago, dthedj said:

So for each of my drives, I need to add "1, 200" in SMART Attribute Notifications and click APPLY?

Only on the WD drives.

You can click on SMART (👎) warning after you decide what to do about it and then Acknowledge it from the popup. It will warn again if any monitored attributes increase.

UDMA_CRC_Error_Count is logged by the drive firmware when it receives inconsistent data (checksum). This is a problem communicating with the drive, often just a loose or maybe bad cable. It often won't cause I/O error since the data is resent. And I/O error often won't cause CRC error since the drive doesn't receive any data to checksum. I usually just Acknowledge the occassional CRC error. If it is increasing frequently you need to check connections.

Disk4 has a lot of these, but maybe they aren't occurring now. It also has a single Runtime_Bad_Block, probably OK for now.

Disk7 has a single Reported_Uncorrect, probably OK for now.

Neither drive has had any self-tests. You might consider running Extended self-test on both.

Disk9 is just disabled and will remain so until rebuilt, or New Config resets that.

If you New Config the repaired disk and rebuild parity, there would be less to restore from backup. You could just delete the lost+found folder

10 hours ago, trurl said:

If you New Config the repaired disk and rebuild parity, there would be less to restore from backup. You could just delete the lost+found folder

Could you please let me know how to proceed with New Config disk 9?

Thanks

Tools - New Config - Retain All - Apply.

In Array Devices, your disks will be assigned as before. Assign the repaired disk as disk9. Start the array to begin Parity Sync.

https://docs.unraid.net/unraid-os/using-unraid-to/manage-storage/array/array-health-and-maintenance/#reset-the-array-configuration

1 hour ago, trurl said:

Tools - New Config - Retain All - Apply.

In Array Devices, your disks will be assigned as before. Assign the repaired disk as disk9. Start the array to begin Parity Sync.

Sorry but with what I just experienced, I'm nervous about losing the data of the other disks, for which I don't have backups.

Is there a possibility that the New Config process make the data of my other disks unavailable?

Should I backup data before to proceed?

Thanks

31 minutes ago, dthedj said:

Sorry but with what I just experienced, I'm nervous about losing the data of the other disks, for which I don't have backups.

Is there a possibility that the New Config process make the data of my other disks unavailable?

Should I backup data before to proceed?

Thanks

New Config does not touch the existing content of any data drives so any existing data on them remains as it was before doing the New Config.

8 hours ago, itimpi said:

New Config does not touch the existing content of any data drives so any existing data on them remains as it was before doing the New Config.

OK, then no worry about the warning "All existing data on this device will be OVERWRITTEN when array is Started" => This will only erase the parity drive, right?

Edited April 8Apr 8 by dthedj

Correct, "this device" is referring to the parity drive.

The parity sync is completed and array seams to work normally. See latest Diagnostics file attached.

Now I need to restore my data from the backups. I guest the easiest would be to copy the backups from my PC to the unRAID Shares over the network.

unraid-diagnostics-20260410-0915.zip

If your backups are on you PC, over the network would be simplest.

If your backups are on external drives, Unassigned Devices plugin is another approach.

I have completed restoring data from backups.

Thank you all for your support, especially trurl and itimp!

There is only one remaining thing to fix: my Plex server can no longer start.

I tried rebooting my unRAID server but always get "Execution error - Server error"

Any idea what I should do to fix this?

Server Log - Plex error.txt

Apr 12 17:44:34 unRAID rc.docker: Plex-Media-Server: Error response from daemon: error gathering device information while adding custom device "/dev/dvb": no such file or directory

Seems like it is configured to include a tuner but doesn't find one.

Yes, I have a tuner card that I removed during troubleshooting but It's now back in the PCI slot.

I think that the tuner appears in the system PCI devices list:

...

[109e:036e] 09:00.0 Multimedia video controller: Brooktree Corporation Bt878 Video Capture (rev 02)

[109e:0878] 09:00.1 Multimedia controller: Brooktree Corporation Bt878 Audio Capture (rev 02)

...

How can I reset Plex settings so it finds the tuner?

PCI devices log.txt

Edited April 12Apr 12 by dthedj