A method includes determining an acceptable site failure number for storing a set of encoded data slices based on available sites and storage units within the available sites. The method further includes determining dispersed storage error encoding parameters based on the acceptable site failure number, wherein the parameters includes a decode threshold number and a total width number. The method further includes encoding, in accordance with the parameters, a data segment of data to produce the set of encoded data slices. The method further includes generating a slice mapping based on the acceptable site failure number, the available sites, and the storage units within the available storage units within the available sites. The method further includes sending, based on the slice mapping, the set of encoded data slices to at least some of the storage units within at least some of the available sites for storage therein.