I don't think the title is quite descriptive enough.

 

I have a primary cache pool of several drives that's explicitly for files.  I also created a separate secondary btrfs formated cache pool with its own singular non-redundant ssd for docker appdata. Plex has just about filled it up with its database. I'm at 93% capacity. I would just add another drive and extend the pool, but I'm all out of SATA ports. So I bought another drive twice the capacity to replace it. 

 

My question is, what's the best/proper procedure for replacing that drive? Do I set the 'appdata' share to move everything to the array, remove the drive, install the new one, start the array, and move all the files back? I fear if anything goes wrong all my containers are gonna get corrupted or not work. 

Your method should work, but you will need to disable the docker and possibly vm services, not just stop the containers, to ensure there are no files in use while the moves are being done. You will know the service is stopped when there is no docker tab available in the GUI when the array is started. Everything must stay stopped until the new drive is in place with all files back in the same path.

 

You can use the built in mover function, but it would probably be much faster to use the Dynamix File Manager plugin to copy all the files to your temporary location on the array.

 

I would copy rather than move, that way you have a full backup.