1. In a dispersed storage network (DSN) that includes a plurality of storage units, wherein the plurality of storage units support a plurality of virtual storage vaults, wherein a first virtual storage vault of the plurality of virtual storage vaults is supported by a first set of storage units of the plurality of storage units, and wherein the first set of storage units is a sub-set of the plurality of storage units, a method comprises: receiving, by at least some of the plurality of storage units, a request to transfer a copy of a set of encoded data slices from two or more source virtual storage vaults of the plurality of virtual storage vaults to a destination virtual storage vault of the plurality of virtual storage vaults, wherein a data segment of data is dispersed storage error encoded to produce the set of encoded data slices; obtaining, by each storage unit of the at least some of the plurality of storage units, a slice transfer map that, for the set of encoded data slices, identifies the two or more source virtual storage vaults; determining, by each storage unit of the at least some of the plurality of storage units, whether the each storage unit supports one of the two or more source virtual storage vaults; for each supporting storage unit that supports one of the two or more source virtual storage vaults, determining, by the each supporting storage unit and based on the slice transfer map, a sub-set of encoded data slices of the set of encoded data slices that is stored within the one of the two or more source virtual storage vaults by the each supporting storage unit; and sending, by the each supporting storage unit, the sub-set of encoded data slices to a corresponding storage unit of the plurality of storage units that is supporting the destination virtual storage vault.