A method for rearranging data blocks in a data storage system when adding new storage devices to create an expanded data storage system. A temporary configuration is selected for which the exchange of one or more data blocks between the temporary configuration and the source configuration produces the destination configuration before identifying and exchanging data blocks between the temporary configuration and the source configuration to produce the destination configuration. A single data element transfer chain embodiment provides superior performance in an embodiment that maintains (does not reduce) the source array data storage efficiency at the destination array after scaling. When adding a single new device to an existing array, the required data movement is minimized and does not exceed the capacity of the new device.