关键词: 固态硬盘（SSD）, 擦除次数, 二次写

Abstract: As the store component of SSD, NAND flash requires erasing a block before writing pages in it, naming it write once memory. The lifetime of SSD is limited to the number of erasures issued to flash cells in SSD. Thus, reducing erasure counts is important for providing highly reliable SSD. This paper proposes a difference and compression based encoding scheme to enable second write to flash pages which are already written once of the SSD, decreasing the erasure time and increasing the lifetime of SSD. This scheme first calculates the differences between existing written data in a physical page and the new data to be written, then it compresses the differences information and encodes the compression result. The scheme writes the encoded data into pages which still hold writable bits, by which the twice-write of SSD is realized. The experiment results show that the proposed scheme effectively reduces erasure counts in frequent data update application.

Key words: solid state drives (SSD), erasure number, write twice