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