text: **3.10 Storage pool configuration**
  
  The storage pool is at the center of the many-to-many relationship between the MDisks and 
  the volumes. It acts as a container of physical disk capacity from which chunks of MDisk 
  space, known as*extents,*are allocated to form volumes presented to hosts. 
  
  MDisks in the Storwize V7000 are LUNs that are assigned from the back-end storage 
  subsystems to the Storwize V7000. There are two classes of MDisks: managed and 
  unmanaged. An unmanaged MDisk is a LUN that is presented to IBM SAN Volume Controller 
  by back-end storage, but is not assigned to any storage pool. A managed MDisk is an MDisk 
  that is assigned to a storage pool. An MDisk can be assigned only to a single storage pool. 
  
  Storwize V7000 clustered system must have exclusive access to every LUN (MDisk) it is 
  using. Any specific LUN cannot be presented to more than one Storwize V7000 cluster. Also, 
  presenting the same LUN to a Storwize V7000 and a host is not allowed. 
  
  One of basic storage pool parameters is the extent size. All MDisks in the storage pool have 
  the same extent size, and all volumes that are allocated from the storage pool inherit its 
  extent size. 