Hi, a disk in my array began showing errors in the ERRORS column and there were a bunch of logs in syslog showing read errors, unRaid still showed it as a healthy drive though.  I ran a long SMART scan and that showed that "Errors occurred".

 

I followed "The Procedure" as documented in the wiki (with slight difference):

Quote

 

Power down

Install the new drive

Power on

Assign the new drive in the slot of the old drive

Go to the Main -> Array Operation section

Put a check in the Yes, I'm sure checkbox (next to the information indicating the drive will be rebuilt), and click the Start button

The rebuild will begin, with hefty disk activity on all drives, lots of writes on the new drive and lots of reads on all other drives

All of the contents of the old drive will be copied onto the new drive, making it an exact replacement, except possibly with more capacity than the old drive.

 

The array has just finished rebuilding but has not restored the data that was on the failed drive, is that right?!

Luckily I still have the old drive as an unassigned drive and can access the files from it, but I was expecting the rebuild to actually restore the files that were on the removed drive.

 

What did I do wrong?

Those look like the right steps.   If you are sure that is exactly what you did you should try clicking on the drive in the Main tab and run the option to check the file system.  

 

A common mistake (despite the warnings) is to add an additional step of formatting the drive not realizing this is not part of the recovery procedure and will update parity  to indicate there is an empty file system on the drive.

 

43 minutes ago, petecemi said:

The array has just finished rebuilding but has not restored the data that was on the failed drive, is that right?!

There is no separate restore step - data should be restored as part of the rebuild.   In fact it will be set to what was shown on the emulated drive before the rebuild was done!  The rebuild process is not aware of data and is merely working at the physical sector level restoring them to what it thinks should be their current content regardless of whether it is part of a file or not.

43 minutes ago, petecemi said:

Luckily I still have the old drive as an unassigned drive and can access the files from it, but I was expecting the rebuild to actually restore the files that were on the removed drive.

Copying the data back is probably the easiest way forward if the file system check did not result in your data being shown again.

Thanks for the response, I stopped the array and started it in Maintenance mode then checked Disk 8 (with -n flag) but it does not show any of the files that were on the old drive.

 

I did not format the fresh drive, I just selected the dropdown for Disk8 and changed it from the old drive to the new one and then checked the box before starting the array.  The indicator showed that the drive was emulated during rebuild, but it did not show any files, I did add some new files onto the drive during rebuild.

 

I will copy the files from the old drive into the share for now, but somewhat worried if this happens again in future.

 

If you haven't rebooted since the rebuild you should post the diags, might provide a clue on what happened.

Sure thing, I saved diags just after the 'rebuild'

tower-diagnostics-20190925-1008.zip

Disk8 was unmountable and you formatted it, formatting deletes all data, correct procedure would be running a filesystem check.

 

Also Parity2 had some sync errors, which suggests Parity1 could also have some, and possibly the reason for the disk being unmountable.

 

Parity needs to be 100% in sync for a rebuild to be successful.

Edited September 25, 20196 yr by johnnie.black

Ah, thank you very much for the help!

 

So I should have formatted it outside the array and then replaced the drive in the array?  I shall be more careful in future :-)

3 minutes ago, petecemi said:

So I should have formatted it outside the array

No, formatting is never part of a rebuild, you'd wait for the rebuild to finish and then run a filesystem check (or do it on the emulated disk before rebuilding, since what shows on the emulated disk is what will be on the rebuilt disk)