1. A method comprises: performing, by at least one processing device, a first portion of a dispersed storage error encoding function on streaming data to produce a plurality of sets of a threshold number of encoded data slices, wherein the dispersed storage error encoding function includes parameters that define a total number of encoded data slices to be created per set and the threshold number as the minimum number of encoded data slices of a particular set to recover a corresponding portion of the streaming data, and wherein a difference between the total number and the threshold number corresponds to a redundancy number; alternatingly, by the at least one processing device, establishing a write only mode for a first memory of a dispersed storage network (DSN) and a second memory of the DSN; writing, by the at least one processing device, sets of the plurality of sets of the threshold number of encoded data slices to the first memory when the first memory is in the write only mode; writing, by the at least one processing device, alternate sets of the plurality of sets of the threshold number of encoded data slices to the second memory when the second memory is in the write only mode; when the first memory is not in the write only mode, reading, by a second processing device, the sets of the plurality of sets of the threshold number of encoded data slices from the first memory; performing, by the second processing device, a second portion of the dispersed storage error encoding function on the read sets of the plurality of sets of the threshold number of encoded data slices to produce sets of redundancy encoded data slices; and writing, by the second processing device, the sets of redundancy encoded data slices to a third memory of the DSN.