A method for execution by a computing device of a dispersed storage network (DSN) to generate memory mapping of logical DSN addresses to storage units of the DSN. The method begins by equally dividing a namespace among groups of storage units of the DSN to produce a set of namespace sections. The method continues by for a first group of storage units, determining storage capacity for each storage unit of the first group of storage units, determining a total storage capacity for the first group of storage units, for a storage unit of a first group of storage units, determining a namespace fraction based on the storage capacity of the storage unit of the first group of storage units and on the total storage capacity and allocating a portion of the first namespace section based on the namespace fraction to the storage unit of the first group of storage units.