A method for execution by a dispersed storage and task (DST) processing unit that includes a processor includes receiving a data object for storage in the DSN via a network. Available storage unit data is generated, indicating a subset of a plurality of storage units of the DSN that corresponds to a plurality of available storage units. A shortened encoding matrix is generated based on an original encoding matrix and the available storage unit data. A size of the shortened encoding matrix is based on a number of storage units in the plurality of available storage units. A plurality of encoded slices is generated, each for transmission to one of the plurality of available storage units via the network, by performing an encoding function on the shortened encoding matrix and the data object.