Huanhuan Tian, Jiewen Tang, Jun Li, Zhibing Sha, Fan Yang, Zhigang Cai, Jianwei Liao
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引用次数: 0
摘要
考虑到 3D NAND 闪存具有工艺变化(PV)的新特性,这会导致闪存块不同层之间的原始误码率(RBER)不同。本文通过考虑 3D NAND 闪存中层与层之间的 PV 因素,以及程序/擦除(P/E)周期和数据保留时间等因素,建立了一个估算闪存单元保留误差的数学模型。然后,根据纠错开销将 3D NAND 闪存中的闪存块层划分为盈利和不盈利两类。在了解三维 NAND 闪存中不同层的保留误差变化后,我们设计了一种数据放置机制,根据数据热度和各层的纠错开销,将写入数据映射到合适的闪存块层上,以提高三维 NAND 闪存的读取性能。实验结果表明,我们提出的保留误差估算模型的平均 R2 值为 0.966,验证了模型的准确性。根据估算的各层滞留误差率,与针对 3D NAND 闪存滞留误差的最先进方法相比,所提出的数据放置机制可显著降低平均 29.8% 的读取延迟。
Modeling Retention Errors of 3D NAND Flash for Optimizing Data Placement
Considering 3D NAND flash has a new property of process variation (PV), which causes different raw bit error rates (RBER) among different layers of the flash block. This paper builds a mathematical model for estimating the retention errors of flash cells, by considering the factor of layer-to-layer PV in 3D NAND flash memory, as well as the factors of program/erase (P/E) cycle and retention time of data. Then, it proposes classifying the layers of flash block in 3D NAND flash memory into profitable and unprofitable categories, according to the error correction overhead. After understanding the retention error variation of different layers in 3D NAND flash, we design a mechanism of data placement, which maps the write data onto a suitable layer of flash block, according to the data hotness and the error correction overhead of layers, to boost read performance of 3D NAND flash. The experimental results demonstrate that our proposed retention error estimation model can yield a R2 value of 0.966 on average, verifying the accuracy of the model. Based on the estimated retention error rates of layers, the proposed data placement mechanism can noticeably reduce the read latency by 29.8% on average, compared with state-of-the-art methods against retention errors for 3D NAND flash memory.
期刊介绍:
TODAES is a premier ACM journal in design and automation of electronic systems. It publishes innovative work documenting significant research and development advances on the specification, design, analysis, simulation, testing, and evaluation of electronic systems, emphasizing a computer science/engineering orientation. Both theoretical analysis and practical solutions are welcome.