I was reading through the documentation for replacing/upgrading disks. I was just curious about a situation not mentioned. If you have a disk fail but have sufficient space on the remaining disks, can the parity disk rebuild the missing data to the existing disks, or does the failed disk NEED to be replaced in order to rewrite the data?

This is not an authoritative answer, but I believe you should not have any problem copying data from the failed drive to the other drives, except that performance will be very poor.  Since it is reconstructing the data of the failed drive by reading all of the other drives, the copy would consist of reading all drives, then writing to the parity and destination drive, forcing a lot of head movement on the parity and destination drive.  It should work, but slowly.

 

The unRAID rebuild process only rebuilds a failed drive onto a replacement drive.

 

I was reading through the documentation for replacing/upgrading disks. I was just curious about a situation not mentioned. If you have a disk fail but have sufficient space on the remaining disks, can the parity disk rebuild the missing data to the existing disks, or does the failed disk NEED to be replaced in order to rewrite the data?

If you wanted to remove the failed disk from your array you could do exactly as you said.

First copy all the files from the failed disk to a working disk.

Then, stop the array, go to the drive assignment web-page and un-assign the failed drive.

Shut down the array and unplug the bad drive.

Power up the unRaid array and stop it once more,  then, check the checkbox that says "I'm sure" and use the "Restore" button to initialize the array configuration. That will completely rebuild parity without the drive you are removing.

 

Note: until your parity is re-calculated on the drives after removing the failed drive you are NOT protected from a second failure of a drive.

 

The whole process will take quite a few hours.  You certainly won't hurt anything to copy critical files from the failed drive to a working drive.  Expect that to take a while.

 

Joe L.