I have an drive that had in my array at one point and removed it. I never used it for anything else but its showing up in unassigned devices but I am unable to do anything to the drive but "Pre-clear" it. I dont want to zero out my entire drive thats going to take 3 days to do. Why am I unable to utilize a format disk call and just add it back to my array?

A disk can only be added to the array without affecting parity if it is Clear (i.e. all zeroes).  The drive either needs to be pre-cleared before adding it or Cleared after adding it.  

IF I recall correctly, you have to change this setting when you want to do formatting type operations:

 

You can find these settings on the MAIN tab:

That's unrelated to the situation, if he wants to add a drive back into the array formatting prior to that is not going to do any good.

20 hours ago, BIGtoeknee said:

Why am I unable to utilize a format disk call and just add it back to my array?

 

Because formatting a disk only rewrites the file tables.  The reminder of the disk still contains the contents of all the files previously stored on the disk--- Even some of the files that have been previously deleted!   If fact if you preclear the disk using the Unassigned Devices Preclear plugin and then format the disk, Unraid will have to clear the disk (again) before adding it to the array.  If you just preclear the disk with the plugin, Unraid will accept the disk into the array without clearing it but then require that it be formatted.  This will take less than five minutes and the disk will be ready to use.

 

EDIT:  If you watch what is happening when you format a precleared disk, you will see writes to the parity disk(s) as the parity is being updated with the information being written to construct the disk's format tables.

Edited February 13, 20251 yr by Frank1940