I'm confused my searches and reading on this subject.  I was running dual parity with 8TB drives.  Just replaced with 2x 10TB drives, they are rebuilding parity now. I have the 2x old 8TB drives to be added into the array.  Once the parity rebuild is complete. can I just add these drives in as data drives?  Do they have to be reformatted?  Do I have to preclear? 3x Preclear cycles takes around 5-6 days (10TB took 6.5 days).  These drives were working fine, it doesn't seem necessary to run the preclear on them again.  I'm attaching a pdf with my Unraid Main page from the GUI if that helps visualize this better.

 

I appreciate any help.  Thank you very much.

Orcrist_Main.pdf

Wait until parity has been rebuilt.

 

Now here is my opinion about those two old 8TB parity drives.  There is no reason to run any Preclear cycles on those drives.  IF they did not have any problems as the parity drives, preclearing them will not find any problem. 

 

If has been a while since I added new data drives but here is a description of how to do it  from the Manual:

 

      https://wiki.unraid.net/UnRAID_6/Storage_Management#Adding_disks

 

This describes the process and what you can expect to be happening.   One thing that is not spelled out is that you will continue to have access to the array while the clearing of the drives is going on.  (I seem to recall that formatting will now take place automatically when the clearing operation has been completed. But, if it doesn't, formatting only takes a minute of two...)