I have a similar situation and instead of starting a new thread, I'm hoping I can put the question here.
I'm also a new unraid user and I've set up a test server using 2 old 1TB drives I had lying around. One was assigned the parity and one was used as a data drive in the array. I've set up the shares and a few docker containers along the way. I'm now comfortable with the set up that I would like to add the real drives that I will be using on the new server. I've purchased 2 x 18TB drives and I've already replaced the 1TB parity drive with one of the 18TB drives. I've successfully completed a parity check. Now I'm trying to figure out what is the easiest/quickest way to replace the 1TB data drive with the other 18TB drive. I've pre-cleared the 18TB drive already. But here's where I'm not sure what's the best way to replace the 1TB drive.
I've read that I can simply shut down the server, remove the 1TB data drive, and stick in the 18TB pre-cleared drive. The server is supposed to be able to rebuild the array on the new 18TB drive. But my question is... with only 1 data drive in the array (which would get removed), is that possible?