1. A method of operating a re-programmable non-volatile memory system having its memory cells organized into distinct blocks of simultaneously erasable cells, comprising: receiving data from outside the memory system for storage in the memory system, designating a first group of one or more blocks of memory cells for storage of the received data, generating records of characteristics of individual ones of the first group of blocks of memory cells, writing the received data into a first group of blocks of memory cells but not including the generated records of characteristics of said first group of blocks of memory cells, writing the generated records of characteristics of individual ones of the first group of blocks of memory cells into a second group of one or more blocks of memory cells but without including the received data.