774 Implementing the IBM Storwize V7000 with IBM Spectrum Virtualize V8.2.1
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.
Data reduction pool
Data Reduction pools are specific types of pools where more control over volumes capacity is 
given to specific hosts (for example VMware VAAI/VASA/VVOL, Microsoft ODX). These hosts 
are able to return unused space for reuse. With standard pools, the system is not aware of 
any unused space on host-allocated volumes. See also “Data reduction”.
Data reduction savings
See “Capacity” on page 771.
Dependent write operation
A write operation that must be applied in the correct order to maintain cross-volume 
consistency.
Directed maintenance procedure
The fix procedures, which are also known as directed maintenance procedures (DMPs), 
ensure that you fix any outstanding errors in the error log. To fix errors, from the Monitoring 
window, click Events. The Next Recommended Action is displayed at the top of the Events 
window. Select Run This Fix Procedure and follow the instructions.
Discovery
The automatic detection of a network topology change, for example, new and deleted nodes 
or links.