text: **Cross-volume consistency**
  A consistency group property that ensures consistency between volumes when an 
  application issues dependent write operations that span multiple volumes. 
  
  **Data consistency**
  Data consistency is a characteristic of the data at the target site where the dependent write 
  order is maintained to ensure the recoverability of applications. 
  
  **Data deduplication**
  Data deduplication is a method of reducing storage needs by eliminating redundant data. 
  Only one instance of the data is retained on storage media. Other instances of the same data 
  are replaced with a pointer to the retained instance. 
  
  **Data encryption key**
  The data encryption key is used to encrypt data. It is created automatically when an 
  encrypted object, such as an array, a pool, or a child pool, is created. It is stored in secure 
  memory and it cannot be viewed or changed. The data encryption key is encrypted by using 
  the master access key. 
  
  **Data migration**
  Data migration is the movement of data from one physical location to another physical 
  location without the disruption of application I/O operations. 
  
  **Data reduction**
  Data reduction is a set of techniques that can be used to reduce the amount of physical 
  storage that is required to store data. An example of data reduction includes data 
  deduplication and compression. See also “Data reduction pool” and “Capacity” on page 771. 