1. A method of operating a re-programmable non-volatile memory system, wherein data are stored in a plurality of distinct blocks of data storage elements, comprising: dividing a logical address range of data into a plurality of distinct units of addresses, transforming the data of the units in a manner that results in at least some of the transformed units individually containing a different amount of data than existed prior to the transformation, storing the transformed data of the units in one or more of the storage element blocks, and identifying the storage locations of the transformed data of individual units by at least one data group having boundaries coincident with boundaries of the transformed unit.