1. A method for execution by a distributed storage (DS) storage unit, the method comprises: receiving an encoded slice of a plurality of encoded slices, wherein the plurality of encoded slices was generated from a data segment using an error encoding function; determining whether the encoded slice is to be sub-sliced using a sub-slicing encoding function; when the encoded slice is to be sub-sliced, generating a plurality of encoded sub-slices from the encoded slices using the encoded sub-slicing encoding function; and outputting the plurality of encoded sub-slices to a plurality of DS storage units.