I've got three WD 12TB disks: 2 data and 1 parity. I would like to stage a hard drive failure to test both the rebuild process and how well the information is restored.

Is it possible to lose a parity disk and rebuild that? As far as I'm aware it would be one of the data disks I would have to wipe

If anyone could guide me through the process of emulating a HDD failure I would be extremity grateful.
Thanks in advance

You can simulate any disk failing by doing the following:

• stop array
• unassign the disk
• start the array to commit the change and make Unraid ‘forget’ the old assignment.   If the disk was a data drive Unraid will show it as being emulated (i.e. its contents still available) using the combination of parity plus other data drives.   If a parity drive then Unraid will now simply show the array as unprotected..
• stop the array
• assign the disk to be rebuilt (data or parity it does not matter)
• start the array to commit the change and start the rebuild.

Followed your advice and it's started the rebuild process. Easier than I thought it would be.
Could I wipe the disk (in a Windows system) once I've unassigned it? The idea being that I'm 100% sure the data is gone and can fully evaluate the recovery process. Or, is this superfluous; does the rebuild process write at a sector level?
Thank you very much for your help, itimpi 🙂

Edited October 16, 20205 yr by TekWarfare

That is up to you.    The rebuild process involves re-writing every sector on the drive so in that sense it is superfluous.    However you may want to prove this to yourself .

 

So I made an attempt to do this before I followed your advice and it resulted with all my files being placed in a "lost+found" folder on the 'replacement' drive. I did have to run a file system repair with -l, -n and no switch as before that it was complaining of no file system.

As this rebuild was meant to write on a per-sector level I assumed it would have restored data in its original form - how it was back when I did the parity sync. This hasn't been the case. I'm at a loss as to what it has actually been doing for the past day then.

 

Is there a way to rebuild the array again so my files are in the correct location?

That should not happen as long as the following are true:

• Parity is valid
• before the rebuild the ‘emulated’ drive mounts with no problems and shows all your files