A processing module of a computing device alternatingly sends a stream of data to a first or second processing device. When receiving the stream of data, the first processing device performs a first portion of a dispersed storage error encoding function on the received stream of data to produce a plurality of sets of a threshold number of slices and writes the plurality of sets of the threshold number of slices into first memory of a dispersed storage network (DSN). When not receiving the stream of data, the first processing device reads the plurality of sets of the threshold number of slices from the first memory, performs a second portion of the dispersed storage error encoding function using the plurality of sets of the threshold number of slices to produce a plurality of sets of redundancy slices, and writes the plurality of sets of redundancy slices into second DSN memory.