基于LDPC读延迟的刷新和副本结合策略优化方案

Policy Optimization Scheme of Refresh and Duplication Combination Based on LDPC Read Delay

针对闪存存储器的密度增大和容量增加导致可靠性下降的问题,提出了一种基于LDPC读延迟的刷新和副本结合策略优化方案。通常,原始策略是在闪存存储器上加一个LDPC码模块,使用硬解码和软解码对数据进行纠错。而传统的刷新策略是在原始策略的基础上,在LDPC软解码未能纠错时,使用刷新策略对其进行纠错。本方案基于LDPC软解码7个量化级别的特性,并以此为判定条件,采用分析对比的方法确定刷新的条件是量化级别到达3,副本的条件是级别达到5,将两种方式合理地应用在LDPC软解码方式中。与前两种策略相比,所提方法缩短了闪存存储器的平均响应时间,在一定程度上提升了闪存存储器的读取性能。在模拟器disksim+ssd的扩展平台上进行仿真,实验结果表明,相比原始策略,该方案平均响应时间均值降低了10%;与传统的刷新策略相比,延长了闪存存储器的寿命。

Aiming at the problem of reliability degradation caused by the increase of the density and capacity of flash memory,an optimization scheme of refresh and copy combination strategy based on LDPC read delay is proposed.In general,the original strategy is to add LDPC code module to flash memory and use hard and soft decoding to correct data errors.The traditional refresh strategy is based on the original strategy,when the LDPC soft decoding fails to correct the error,the refresh strategy is used to correct the error.The scheme is based on the characteristics of LDPC soft decoding 7 quantitative levels,and takes this as the judgment condition,using the method of analysis and comparison to determine that the condition of refresh is level 3,the condition of the copy is level 5,and the two methods are reasonably applied in the LDPC soft decoding mode.Compared with the previous two strategies,the average response time of flash memory is reduced,and the read performance of flash memory is improved to a certain extent.Simulation is performed on the extended platform of the simulator disksim+ssd,and experimental results show that,the average response time of this scheme is 10%shorter than that of the original strategy,and its flash memory lifetime is prolonged compared to traditional refresh strategies.