Logical volume management
The LVs can be grown by concatenating more PEs from the pool.  Some volume managers allow LV shrinking; some allow online resizing in either direction.  Changing the size of the LV does not necessarily change the size of a filesystem on it; it merely changes the size of its containing space. A file system that can be resized online is recommended because it allows the system to adjust its storage on-the-fly without interrupting applications.