Hello everyone!

I have stumbled upon a rather frustrating situation. I currently have a 12TB HDD that is dying. I wanted to replace this dying disk with a new, fresh one I bought from Amazon. So I went through the normal process of replacing a disk.

I stopped the array, unassigned the target disk (Disk 8), removed the old disk (I have hotswap support, so I did not shut down the server), added the new disk at the same stop, assigned the new disk to the missing disk, started the array in maintenance mode and began a sync.

The issue now is that the new drive catastrophically failed after about 1 minute of use. By the sound it was making I guess the read/write head was scraping the disk. Either way, the drive was unmounted and I can no longer see the driver being detected, neither in Unraid nor in the BIOS.

Now since the new drive is unusable, I would like to read the old dying HDD to the array. My thought is that a dying HDD is still better than emulating the disk. The issue I am facing now is that since I already started the sync with the old drive, I cannot readd the old drive, since unraid now expects an 18tb drive in that slot. But my old drive should still hold the correct data, as I have started the array in maintenance mode for the sync.

So with the context out of the way, my questions would be:

1. Can I somehow trick unraid into letting me assign the old disk into the old slot?

2. And if 1 is possible, can I use the drive without rebuilding it? I think using the drive should be no problem, as I started the array in maintenance mode for the sync, so no new data should have been added to the array during this time.

Thank you in advance for your help!

bm-dell01-diagnostics-20251210-1720.zip

Start the array in normal mode with nothing assigned to that slot and post new diagnostics.

Sure, here are the diagnostics.

bm-dell01-diagnostics-20251211-0828.zip

You can do a new config (tools - new config - keep all - apply), then assign the old disk8 and check "parity is already valid" before array start.

You'll then need to run a correcting parity check but it should find just a few errors.