Compression type defines the compression method the backup application will use during backup job (for the corresponding backup set).
There are three compression types available for the user to select:
By default, newly created backup sets are configured to use [Fast] compression type.
For File, VMware ESXi/vCenter, and Hyper-v backup sets. If OpenDirect, Granular Restore, or Run Direct is enabled, then the compression type is to "No Compression" in order to ensure optimal restore performance.