| Flash memory has been widely used in various fields because of its high performance,low power consumption and other characteristics.The change of flash memory structure leads to the gradual increase of data error rate.In view of the accuracy requirements of users,the reliability of flash memory has become the focus of research.Flash memory mainly uses duplication and erasure correction code to ensure the reliability of data.The duplication method recovers faster but requires more space.Erasure correction code method has higher system reliability in the same environment,but will cause more time overhead.At present,the commonly used erasure code in flash memory is Low-density Parity-check code(LDPC),which has strong error correction ability and is used in flash memory.However,direct use of its decoding method will cause large delay.In view of the above contents,this paper studies the combination of replica and LDPC code,specifically including the combination of duplication and refresh,the combination of duplication and LDPC soft decoding,and the combination of duplication and LDPC mixed decoding,as follows:(1)A scheme is proposed to apply duplication and refresh to the quantization level of LDPC code(RAD).This scheme analyzes the decoding delay caused by seven quantization levels involved in LDPC soft decoding.By adopting duplication and refresh strategies respectively when reaching the quantization level that causes a large delay,the average response time of flash memory is reduced to a certain extent,and the life of flash memory is improved.(2)A scheme combining duplication and LDPC soft decoding(IDSD)is constructed.The IDSD scheme studies hot data,and considers that the decoding ability of LDPC code will gradually increase with the improvement of quantization level,but the delay caused by it will also increase.When the quantization level of LDPC soft decoding is required to reach 1 for error correction,the error data shall be marked.When the number of pages of the error data reaches half of the number of pages contained in the block,the duplication shall be used for recovery.(3)A hybrid decoding scheme of duplication and LDPC(IDHSD)is proposed.The IDHSD scheme focuses on the hot data,and considers that the LDPC code soft decoding method will bring higher time complexity.Therefore,the duplication is applied between the hard decoding mode and the soft decoding mode to avoid directly using the soft decoding for error correction,which improves the reliability of the flash memory and the availability of data to a certain extent.The experiment shows that under different loads,the response time of flash memory is different due to the influence of read and write ratio.Compared with the original scheme,the average response time of RAD scheme decreased by 10.1%,the average response time of IDSD scheme decreased by 19.7%,and the average response time of IDHSD scheme decreased by 20.26%.Compared with the traditional refresh strategy,the RAD scheme has extended the life of flash memory,reduced the average response time of IDSD by 9.6%,and reduced the average response time of IDHSD scheme by 10.83%. |
