Hi All,

I’m a beginner Unraid user and I noticed that Disk3 of my array had a red X. My Unraid version is 6.12.13 and I have dual parity drives. I was hoping it was a cable issue, not a drive failure, and I took the following steps as best that I can remember:

1. Powered down my server

2. Reseated the cables on Disk3

3. Powered on the server

4. Stopped the array 

5. Unassigned Disk3

6. Started the array in maintenance mode

7. Stopped the array

8. Assigned Disk3 back 

9. Started the array

10. Formatted Disk3

11. Started data rebuild 

The data rebuild began ok with speeds of 180MB/s but by morning the speeds had slowed to between 100KB/s to 1MB/s and the estimated time to completion was 100 days. Additionally, Disk3 went from a green circle to orange triangle! and says “device contents emulated click to spin down device”. 

Now I suspect I’m having my first drive failure and have a replacement drive available to replace it but I’m concerned I may take the wrong next steps.

I’ve included my diagnostics and would appreciate your help. Thank you!

unraid13100-diagnostics-20260124-0908.zip

1 hour ago, LongJohn said:

Formatted Disk3

So you will be rebuilding a formatted disk then.

Diagnostics does show emulated disk3 has 1.4TB used though, so must not have formatted it. I don't know what you think you did at that step.

Looks like disk3 has some SMART issues though. Better if you replaced it.

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

Hi trurl,

Thank you for your help!

15 minutes ago, trurl said:

So you will be rebuilding a formatted disk then.

Ok, that makes sense. It appears I misunderstood data rebuild to mean it would rebuild the drive from parity to achieve the state before disk3 had a red x.

15 minutes ago, trurl said:

Diagnostics does show emulated disk3 has 1.4TB used though, so must not have formatted it. I don't know what you think you did at that step.

After formatting, disk3 showed as empty on the MAIN page. After starting the data rebuild, I watched it filling up from empty on the MAIN page at expected speeds. By morning it had reached 1.4TB used and speeds had dropped. It has not increased from there (nominally perhaps) in over 24 hours.

15 minutes ago, trurl said:

Looks like disk3 has some SMART issues though. Better if you replaced it.

Is it safe to cancel the data rebuild and proceed with replacing the drive? What are the correct steps?

15 minutes ago, trurl said:

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

No other drives show SMART warning ( 👎 ) on the DASHBOARD page.

40 minutes ago, LongJohn said:

Ok, that makes sense. It appears I misunderstood data rebuild to mean it would rebuild the drive from parity to achieve the state before disk3 had a red x.

It would have do this if you do NOT do the format. When you try and do the format you get a dialog warning you that format is not part of a data recovery and will result in loss of the data on that dtive if you proceed.

Hi itimpi, thank you for the additional detail. Does that mean the parity drives no longer have the data that was on disk3 prior to format?

Is it safe to cancel the data rebuild and proceed with replacing the drive? What are the correct steps?

Just now, LongJohn said:

Hi itimpi, thank you for the additional detail. Does that mean the parity drives no longer have the data that was on disk3 prior to format?

Parity holds none of your data! What it does have is the information to enable a failed drive to be reconstituted at the bit level by using the combination of the parity drive and all the other data drives. When you do a format then parity is updated to reflect the format.

It may be possible to recover the data on the drive using a file recovery program such as UFS Explorer on Windows. That software is not free, but it does have a free mode that can show you what the paid for version would recover.

Hi itimpi, that explanation makes sense. Fortunately, I have backups of the data.

However, I'm still stuck in the position of not knowing the correct way forward to end the data rebuild and then replace the drive. My options appear to be:

1. Wait 100 days for the data rebuild to complete. SMART warning indicates this drive has issues - perhaps this isn't the best option. Perhaps it won't be able to complete at all.

2. Pause the data rebuild. I'm not sure what comes after that if not options 1 and 3.

3. Cancel the data rebuild which carries the warning "WARNING: canceling may leave the array unprotected!"

I believe I can find a guide to replacing the drive if you'd please assist me in understanding the choice I should make regarding ending the data rebuild. Thank you again for your help.

It appears that disk3 has reached 1.57TB of data and browsing the disk shows the expected data, albeit only 1.57TB of the nearly 8TB it previously held.

19 minutes ago, LongJohn said:

It appears that disk3 has reached 1.57TB of data and browsing the disk shows the expected data, albeit only 1.57TB of the nearly 8TB it previously held.

That suggests you somehow added 1.57TB to the formatted emulated empty disk.

If you stop and replace the disk, it will rebuild that added 1.57TB onto the new disk. But whatever was on the disk before you formatted it is gone.

Just now, trurl said:

That suggests you somehow added 1.57TB to the formatted emulated empty disk.

In addition to the drive SMART problems, if you were indeed writing a large amount of data while also rebuilding, that is going to slow things down.

7 minutes ago, trurl said:

That suggests you somehow added 1.57TB to the formatted emulated empty disk.

If you stop and replace the disk, it will rebuild that added 1.57TB onto the new disk. But whatever was on the disk before you formatted it is gone.

Thank you, you're right! I forgot to pause a scheduled script to move data. I will stop and replace the disk.