After rebuild from unmountable disk, data was not restored; major data loss. (v6.12.9)

[chris1259]

unRaid v6.12.9

 

9 X 12TB Seagate Exos X14 Drives

 

2 of the drives are parity drives.

 

After upgrading to v6.12.9 from 6.12.8 and rebooting, the server automatically started a parity check. I let it run and it found 11733 errors. After another reboot one of the data disks reported as unmountable. I replaced the drive and the rebuild started; however, i noticed my main network share that was 84% full, now only reported 70% full. The data rebuild finished successfully with zero errors after i replaced the disk. The unmountable disk was tested outside of the server and had no issues, including a full format.

 

Since 2016, i have replaced bad disks before and never lost data. All important data was backed up on other devices, and i should be able to restore most of what i lost from there. I am now trying to understand what happened.

 

Any help is appreciated!

diagnostics-20240401-1203.zip

Edited April 1 by chris1259

[JorgeB]

Unmountable disk is usually fixed by check filesystem, not by replacing the disk, that will just rebuild another unmountable disk, but I don't see any unmountable disk in your diags, did you format it?

[chris1259]

I formatted the unmountable disk outside of the server to confirm no bad sectors were found. I did not return this newly formatted disk to the array.

 

From the link you provided, it sounds like the file system had become corrupted, and i may have been able to fix it.

 

What is unclear to me is the difference between an unmoutable corrupted drive, and a drive that is no longer working. Why does the data rebuild work on a dead drive, but not a drive that was replaced because it was unmountable.

 

Thanks.

[itimpi]

45 minutes ago, chris1259 said:

Why does the data rebuild work on a dead drive, but not a drive that was replaced because it was unmountable.

I think you misunderstand the data rebuild.  What happens after a disk dies depends on the state of the emulated disk.   All rebuild does is make a physical disk match the ‘emulated’ one.   If the emulated disk shows as mountable before the rebuild it will be mountable afterwards, but if it shows as unmountable it will also shows as unmountable after the rebuild..  
 

 That is why we tend to recommend trying to repair an emulated disk before rebuilding as if the physical disk has not actually failed it may still be possible to get most/all the data off it.

[chris1259]

Thank you for the explanation. Thus far, all the drives i have replaced have either failed or gone offline (disabled). In each case, i replaced the disk with a new one and rebuild did the rest. Next time i will place the array in maintenance mode, and review what repair options are available.