Percentage Saved by Storage Efficiency have a difference of 4% per volume even if all data on the volume is copied from another

Applies to

• ONTAP 9
• Storage Efficiency
• Volume-level background deduplication

Issue

All data on the volume is copied from another volume, however, Percentage Saved by Storage Efficiency have a difference of 4% per volume.

                           Vserver Name: Vserver01
                            Volume Name: Vserver01_vol1
                Total User-Visible Size: 47.50TB
                  Snapshot Reserve Used: 42%
      Space Saved by Storage Efficiency: 14.82TB 
 Percentage Saved by Storage Efficiency: 36%  
           Space Saved by Deduplication: 14.82TB
      Percentage Saved by Deduplication: 36%
    Volume Size Used by Snapshot Copies: 1.06TB
               Total Physical Used Size: 27.10TB
               Physical Used Percentage: 54%
        Available Snapshot Reserve Size: 1.44TB
                      Logical Used Size: 40.91TB 
                Logical Used Percentage: 86%
                 Logical Available Size: -
 Logical Size Used by Active Filesystem: 40.91TB
     Logical Size Used by All Snapshots: 3.71PB

                           Vserver Name: Vserver02
                            Volume Name: Vserver02_vol1
                Total User-Visible Size: 47.50TB
                  Snapshot Reserve Used: 332%  
      Space Saved by Storage Efficiency: 14.83TB 
 Percentage Saved by Storage Efficiency: 32%  
           Space Saved by Deduplication: 14.83TB
      Percentage Saved by Deduplication: 32%
    Volume Size Used by Snapshot Copies: 8.30TB
               Total Physical Used Size: 34.50TB
               Physical Used Percentage: 69%
        Available Snapshot Reserve Size: 0B
                      Logical Used Size: 46.83TB 
                Logical Used Percentage: 99%
                 Logical Available Size: -
 Logical Size Used by Active Filesystem: 41.03TB
     Logical Size Used by All Snapshots: 3.04PB