text: **10.6.2 Evaluating compression and deduplication**
  
  To help with the profiling and analysis of user workloads that must be migrated to the new 
  system, IBM provides a highly accurate data reduction estimation tool that supports both 
  deduplication and compression. The tool operates by scanning target workloads on any 
  legacy array (from IBM or third party) and then merging all scan results to provide an 
  integrated system level data reduction estimate. 
  
  The Data Reduction Estimator Tool (DRET) utility uses advanced mathematical and statistical 
  algorithms to perform an analysis with low memory footprint. The utility runs on a host that 
  can access the devices to be analyzed. It performs only read operations so it has no effect on 
  the data stored on the device. 
  
  The following sections provide information about installing DRET on a host and using it to 
  analyze devices on it. Depending on the environment configuration, in many cases DRET is 
  used on more than one host to analyze more data types. 
  
  When DRET is used to analyze a block device that is used by a file system, all underlying 
  data in the device is analyzed, regardless of whether this data belongs to files that were 
  deleted from the file system. For example, you can fill a 100 GB file system and make it 100% 
  used, and then, delete all the files in the file system to make it 0% used. When scanning the 
  block device that is used for storing the file system in this example, the DRET accesses the 
  data that belongs to the files that are deleted. 