Based on a detected data transfer instruction, a computing device within a dispersed storage network (DSN) determines a data transfer synchronization protocol that substantially maintains synchronization of at least the write threshold number of first associated slices (e.g., a first row of encoded data slices) to be transferred from the first set of storage units (SUs) to a second set of SUs based on a substantially same first transfer rate and substantially maintains synchronization of at least the write threshold number of second associated slices (e.g., a second row of encoded data slices) to be transferred from the first set of SUs to the second set of SUs based on a substantially same second transfer rate. The computing device then executes the data transfer synchronization protocol to perform substantially synchronized transfer of respective sets of the plurality of sets of encoded data slices from the first set of SUs to the second set of SUs.