Storage Coding for Wear Leveling in Flash Memories

NAND flash memories are currently the most widely used type of flash memories. In a NAND flash memory, although a cell block consists of many pages, to rewrite one page, the whole block needs to be erased and reprogrammed. Block erasures determine the longevity and efficiency of flash memories. So when data is frequently reorganized, which can be characterized as a data movement process, how to minimize block erasures becomes an important challenge. In this paper, we show that coding can significantly reduce block erasures for data movement, and present several optimal or nearly optimal algorithms. While the sorting-based non-coding schemes require O(n log n) erasures to move data among n blocks, coding-based schemes use only O(n) erasures and also optimize the utilization of storage space.