text: When you add MDisks to pools, you must assign them to the correct storage tiers. It is 
  important to set the tiers correctly if you plan to use the Easy Tier feature. Otherwise, the 
  wrong tier can corrupt Easy Tier algorithm logic and might affect system performance. For 
  more information about storage tiers, see Chapter 10, “Advanced features for storage 
  efficiency” on page 403. 
  
  The storage tier setting can be also changed after the MDisk is assigned to the pool. 
  
  Check the**Externally encrypted**checkbox if back-end storage currently performs data 
  encryption. For details on IBM Storwize V7000 encryption, see Chapter 12, “Encryption” on 
  page 603. 
  
  After the task is completed, click**Close.**
  
  **Note:**If the external storage LUs to virtualize behind the Storwize V7000 contain data and 
  this data needs to be retained, do not use the “Assign to pool” option to manage the 
  MDisks. This option destroys the data on the LU. Instead, use the Import option. For more 
  information, see Chapter 9, “Storage migration” on page 385. 
  
  The external MDisks that are assigned to a pool within IBM Storwize V7000 are displayed in 
  **Pools**→**MDisks by Pools**. 