suppose you have a 100GB volume with one, 50GB LUN in it
- if the volume is thick provisioned, 100GB worth of blocks are set aside (reserved) for that volume by the aggregate
- if the volume is thin provisioned and the LUN has reservation enabled, 50GB worth of blocks are set aside (reserved) for that LUN by the aggregate
- if both, the volume and the LUN are thin provisioned, blocks are provided to the LUN as required/requested (up to 50GB - given that there is enough space in the aggregate)