1. A method for execution by a distributed storage (DS) processing unit, the method comprises: generating a plurality of encoded slices from a data segment using an error encoding function; identifying a plurality of DS storage units for storing the plurality of encoded slices; selecting an encoded slice of the plurality of encoded slices for sub-slicing using a sub-slicing encoding function to produce a selected encoded slice; outputting the plurality of encoded slices to the plurality of DS storage units; and outputting a command to a DS storage unit of the plurality of DS storage units corresponding to the selected encoded slice, wherein the command includes an instruction to sub-slice the selected encoded slice.