I personally would not trust the controller to expand the array. If I had the ports available I would add the new array and then copy everything over. If not, I would use an external 2.5" USB drive to copy everything or use as a backup. If making a backup, I would test restoring the data. Once all this is done, I would use the controller to delete the array that needs to be replaced. Once the new drive is added I would create the new array and copy all the data back or restore from backup.