So the procedure is :
1, I add the UD plugin.
2, I try to empty a larger hdd ,and add it to the array, without adding a parity or a buffer,then start the array.
3, I copy data (in command line with cp or midnight commander )to fill the array to empty another hdd,
4, I stop the array, add the newly emptied disk, without adding a parity or buffer, and start the array.
5,I loop over 3 and 4 till all hdd is added (but still no parity or buffer).
6,Then I need a disk as parity and it should be the largest one in their volume.
Am I understanding it right?