Managing data reduction in storage systems using machine learning

A method is used in managing data reduction in storage systems using machine learning. A value representing a data reduction assessment for a first data block in a storage system is calculated using a hash of the data block. The value is used to train a machine learning system to assess data reduction associated with a second data block in the storage system without performing the data reduction on the second data block, where assessing data reduction associated with the second data block indicates a probability as to whether the second data block can be reduced.