Extending Lifetime of Flash Memory Using Strong Error Correction Coding
Extending Lifetime of Flash Memory Using Strong Error Correction Coding
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DOI：
10.1109/tce.2015.7150595
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发表时间：
2015-05-01
影响因子：
4.3
通讯作者：
Lee, Sunggu
中科院分区：
文献类型：
--
作者：
Kim, Chanha;Park, Chanik;Lee, Sunggu
对基于闪存的存储系统的需求正在上升，因为与硬盘驱动器相比，闪存具有许多优点，例如较低的延迟和抗物理冲击。然而，闪存仅允许有限数量的编程/擦除（P/E）周期，并且在保证数量的P/E周期之后，由于不可校正的错误，数据不能被可靠地检索。给定目标比特错误率，P/E周期的保证数量随着更多比特存储在一个单元中以及随着单元大小按比例缩小而减小。在本文中，一种新的寿命延长机制的闪存，被称为渐进纠错码（G-ECC），提出。G-ECC通过牺牲一小部分存储容量来存储额外的奇偶校验位，从而提供比标准ECC更强的纠错级别。所提出的方法可以延长闪存的寿命的124%，在12%的容量损失的成本。使用附加奇偶校验位必然导致性能损失，这是由于对那些附加奇偶校验位的访问增加以及涉及那些位的垃圾收集操作。因此，提出了减轻这种性能损失的方法;即使在最坏的情况下，这些方法也将性能开销从17%（没有所提出的方法）降低到3%。（一）
Demand for flash memory based storage systems is on the rise because flash memory has many advantages when compared with hard disk drives, such as lower latency and resistance to physical shock. However, flash memory permits only a limited number of program/erase (P/E) cycles, and after the guaranteed number of P/E cycles, data cannot be reliably retrieved due to uncorrectable errors. Given a target bit error rate, the guaranteed number of P/E cycles decreases as more bits are stored in one cell and as the cell size is scaled down. In this paper, a novel lifetime extension mechanism for flash memory, referred to as a gradual error correction code (G-ECC), is proposed. A G-ECC provides a stronger level of error correction than a standard ECC by sacrificing a small portion of storage capacity in order to store additional parity bits. The proposed method can extend the lifetime of flash memory by 124% at the cost of a 12% loss in capacity. The use of additional parity bits necessarily leads to performance loss due to increased accesses for those additional parity bits and garbage collection operations involving those bits. Thus, methods to alleviate such performance loss are proposed; these methods reduce the performance overhead from 17% (without the proposed methods) to 3% even in the worst case.(1)