I replaced one of my 6TB drives yesterday to upgrade and during the rebuild overnight a second drive started reporting over 800,000 read errors which have stopped while the rebuild still continues.

What should my next steps be? I have the original 6TB drive I replaced still, but data has still been written to the array while the rebuild was in progress overnight.

Please post the diagnostics.

Diagnostics attached. Since the failure I've disabled the docker and vm services to limit writes to the array.

Disk 13, sdt is the drive originally replaced for the upgrade.

Disk 8, sdm is the drive that started throwing errors during the rebuild of sdt.

Thank you

orbit-diagnostics-20250825-0911.zip

Looks like this accidentally got marked as solved early morning when submitted. That’s been corrected. Apologies for the mixup.

It's not logged as a disk problem, and SMART looks mostly OK. Replace cables/swap slots for disk8 and try again.

Thank you. Rebuild cancelled and will report back.

Edited August 25, 2025Aug 25 by sidezero

I mistakenly removed Disk 13 from the Unraid GUI and had auto start enabled without realizing. Upon boot up Disk 8 is showing additional read errors and unmountable. Disk 13 is also showing the same but that is expected due to my previous manual removal.

I still have the original Disk 13 available.

Updated diagnostics are attached. I haven't stopped the array to re-add Disk 13 yet at this point from the initial slot swap and boot up/auto start.

orbit-diagnostics-20250825-1546.zip

Just to confirm, did you replace the cables for disk8 as suggested?

1 hour ago, JorgeB said:

Just to confirm, did you replace the cables for disk8 as suggested?

I use an old Norco 4220 case. Since the cables are shared to a backplane I swapped slots on the backplane with another drive before it became unmountable.

Try using a different slot for them; one from a different backplane is applicable. Norcos usually have 4 disks per backplane, swap with another disk if needed.

Eliminate any power splitters in use, too. Use only the connectors on the lead to the PSU per backplane, if you split them, it will cause voltage dips and reset the drive

Aug 25 01:25:51 orbit kernel: sd 2:0:7:0: Power-on or device reset occurred

There are no power splitters in place. When I performed a rebuild I had to purposely purchase an overkill PSU in order to get enough connections for the backplane.

I moved Disk 8 to another slot as requested and I saw the same thing upon boot. Disk 8 and Disk 13 are unable to be mounted and the parity operation kicked off. Disk 8 is currently accumulating millions of errors. Updated diagnostic attached.

orbit-diagnostics-20250826-0847.zip

1 hour ago, sidezero said:

I moved Disk 8 to another slot

Another slot on a different row?

Yep, a different vertical and horizontal row.

Edited August 26, 2025Aug 26 by sidezero

11 minutes ago, sidezero said:

Yep

OK, i'm still leaning power then

The failures seem pretty consistent with Disk 8 despite it being in three different slots now.

With the current issues is there any process where I can re-install the original Disk 13 and then attempt to rebuild Disk 8 instead with the existing parity data?

It still looks more like a power/connection issue, but if you are using another slot in a different row, it could really be the disk, despite the type of logged errors.

If there weren't other changes to the array, you can try this, but it will work if parity is still valid:

-Tools -> New Config -> Retain current configuration: All -> Apply

-Check all assignments and assign any missing disk(s) if needed, including the old disk 13 and a new disk8, replacement disk should be same size or larger than the old one

-IMPORTANT - Check both "parity is already valid" and "maintenance mode" and start the array (note that the GUI will still show that data on parity disk(s) will be overwritten; this is normal as it doesn't account for the checkbox, but it won't be as long as it's checked)

-Stop array

-Unassign disk8

-Start array (in normal mode now), and post new diagnostics

Keep old disk 8 intact for now.

Process followed and updated diagnostics attached. Thank you.

orbit-diagnostics-20250826-1253.zip

Auto didn't detect the filesystem, stop the array, on main click on disk8 (with the disk still unassigned), set the filesystem to xfs, start the array, post new diags.

Drive set to xfs and updated diags attached.

orbit-diagnostics-20250827-0336.zip

OK, now I see the XFS signature, but there are some fs issues, check filesystem for that disk.

Ran a repair on the emulated disk and re-started the array in normal mode to confirm there doesn't appear to be a lost+found directory created on the emulated Disk 8. At this point am I good to re-add the new drive in the disk8 slot and start the array/rebuild?

Edited August 27, 2025Aug 27 by sidezero

If the emulated disk is mounting and the contents look good, you can reassign the new disk to rebuild.

Rebuild is running. Thank you again for all the help.