Abstract Although NAND flash memory has revolutionized how we manage data in modern digital systems, significant improvements are needed in flash-based storage systems to meet the requirements of emerging data-intensive applications. In this paper, we address the problem of NAND aging markers that represent the wearing degree of NAND cells. Since all flash operations are affected by the wearing status of NAND cells, an accurate NAND aging marker is critical to develop flash optimization techniques. From our evaluation study, we first show that the existing P/E cycle-based aging marker ( PeWear ) is inadequate to estimate the actual aging status of NAND blocks, thus losing opportunities for further optimizations. To overcome the limitations of PeWear , we propose a new NAND aging marker, RealWear , based on extensive characterization studies using real 3D TLC flash chips. By considering multiple variables that can affect the NAND cell wear, RealWear can accurately indicate the actual wear status of NAND blocks during run time. Using three case studies, we demonstrate that RealWear is effective in enhancing the lifetime and performance of a flash storage system. Our experimental results showed that RealWear can extend the lifetime of individual NAND blocks by 63% and can reduce the GC overhead by 21%. Furthermore, RealWear significantly mitigates read latency fluctuations, guaranteeing that the read latency can be bounded with at most 2 read retry operations.

中文翻译：

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RealWear：使用 NAND 老化标记提高 SSD 的性能和使用寿命

摘要 尽管 NAND 闪存彻底改变了我们在现代数字系统中管理数据的方式，但基于闪存的存储系统仍需要进行重大改进，以满足新兴数据密集型应用的要求。在本文中，我们解决了代表 NAND 单元磨损程度的 NAND 老化标记问题。由于所有闪存操作都受到 NAND 单元磨损状态的影响，因此准确的 NAND 老化标记对于开发闪存优化技术至关重要。从我们的评估研究中，我们首先表明现有的基于 P/E 周期的老化标记 (PeWear) 不足以估计 NAND 块的实际老化状态，从而失去进一步优化的机会。为了克服 PeWear 的局限性，我们提出了一种新的 NAND 老化标记 RealWear ，基于使用真实 3D TLC 闪存芯片的广泛表征研究。通过考虑影响NAND单元磨损的多个变量，RealWear可以准确地指示运行时NAND块的实际磨损状态。通过三个案例研究，我们证明了 RealWear 在提高闪存存储系统的使用寿命和性能方面是有效的。我们的实验结果表明，RealWear 可以将单个 NAND 块的寿命延长 63%，并将 GC 开销减少 21%。此外，RealWear 显着减轻了读取延迟波动，保证读取延迟最多可以限制为 2 次读取重试操作。通过三个案例研究，我们证明了 RealWear 在提高闪存存储系统的使用寿命和性能方面是有效的。我们的实验结果表明，RealWear 可以将单个 NAND 块的寿命延长 63%，并将 GC 开销减少 21%。此外，RealWear 显着减轻了读取延迟波动，保证读取延迟最多可以限制为 2 次读取重试操作。通过三个案例研究，我们证明了 RealWear 在提高闪存存储系统的使用寿命和性能方面是有效的。我们的实验结果表明，RealWear 可以将单个 NAND 块的寿命延长 63%，并将 GC 开销减少 21%。此外，RealWear 显着减轻了读取延迟波动，保证读取延迟最多可以限制为 2 次读取重试操作。