1. A method for execution by one or more processing modules of one or more computing devices, the method comprising: receiving, over time, a large data file for storage in a dispersed storage network (DSN); determining initial dispersed storage error encoding parameters for storing the large data file, wherein the initial dispersed storage error encoding parameters indicate an error coding number and a decode threshold number, wherein the error coding number indicates a number of encoded data slices that results when a data segment of the large data file is encoded using a dispersed storage error encoding function, and the decode threshold number indicates a minimum number of the encoded data slices that are needed to recover the data segment; encoding, using the dispersed storage error encoding function and during a first time interval of receiving the large data file, a first plurality of data segments of a first portion of the large data file using the initial dispersed storage error encoding parameters to produce a first plurality of sets of encoded data slices; writing, during the first time interval, the first plurality of sets of encoded data slices to storage units of the DSN; monitoring processing of the writing of the first plurality of sets of encoded data slices to produce first write processing performance information; and when the first write processing performance information compares unfavorably to a desired write performance range, adjusting, for a second time interval of receiving the large data file, at least one of the error coding number and the decode threshold number to produce adjusted dispersed storage error encoding parameters.