An Empirical Study of Quad-Level Cell (QLC) NAND Flash SSDs for Big Data Applications

Liang, Shuwen; Qiao, Zhi; Tang, Sihai; Hochstetler, Jacob; Fu, Song; Shi, Wei; Chen, Hsing-Bung

doi:10.1109/bigdata47090.2019.9006406

Cited by 19 publications

(6 citation statements)

References 7 publications

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“…We estimate the endurance limit by dividing the SSD's TBW (terabytes written: the total amount of writes the SSD manufacturer guarantees) by the logical capacity. This estimation is consistent with recent works [21,22].…”

Section: Introductionsupporting

confidence: 94%

“…We implement a capacity-variant SSD on the extended FTLSim [9] from § 2 and use the SSD configuration in Table 2 for our evaluation. However, we set the endurance limit to 500 erases, a typical level for QLC [21,22], and once a block reaches this, it will be mapped out and no longer used in the SSD, effectively reducing the SSD's physical capacity. For the fixed capacity SSD, the SSD is considered to reach its end of life once the physical capacity becomes smaller than its logical capacity: the SSD is considered to have failed once this happens.…”

Section: Case Study On Capacity Variancementioning

confidence: 99%

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Wear leveling in SSDs considered harmful

Jiao

Bhimani

Kim

2022

Proceedings of the 14th ACM Workshop on Hot Topics in Storage and File Systems

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We argue that wear leveling in SSDs does more harm than good under modern settings where the endurance limit is in the hundreds. To support this claim, we evaluate existing wear leveling techniques and show that they exhibit anomalous behaviors and produce a high write amplification. These findings are consistent with a recent large-scale field study on the operational characteristics of SSDs. We discuss the option of forgoing wear leveling and instead adopting capacity variance in SSDs, and show that the capacity variance extends the lifetime of the SSD by up to 2.94×.

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Section: Introductionsupporting

confidence: 94%

Section: Case Study On Capacity Variancementioning

confidence: 99%

Wear leveling in SSDs considered harmful

Jiao

Bhimani

Kim

2022

Proceedings of the 14th ACM Workshop on Hot Topics in Storage and File Systems

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“…These advancements in control mechanisms have paved the way for the successful commercialization of triple-level cell (TLC) and quadruple-level cell (QLC) technologies within the domain of 3D NAND. This achievement has further enhanced the appeal and versatility of this memory technology [9][10][11][12]. However, it is essential to acknowledge that the transition to multilevel cells presents a unique set of challenges, particularly concerning threshold voltage (V TH ) distribution.…”

Section: Introductionmentioning

confidence: 99%

Effect of Noncircular Channel on Distribution of Threshold Voltage in 3D NAND Flash Memory

Go,

Yoon,

Park

et al. 2023

Micromachines

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The instability in threshold voltage (VTH) and charge distributions in noncircular cells of three-dimensional (3D) NAND flash memory are investigated. Using TCAD simulation, we aim to identify the main factors influencing the VTH of noncircular cells. The key focus is on the nonuniform trapped electron density in the charge trapping layer (CTL) caused by the change in electric field between the circular region and the spike region. There are less-trapped electron (LT) regions within the CTL of programmed noncircular cells, which significantly enhances current flow. Remarkably, more than 50% of the total current flows through these LT regions when the spike size reaches 15 nm. We also performed a comprehensive analysis of the relationship between charge distribution and VTH in two-spike cells with different heights (HSpike) and angles between spikes (θ). The results of this study demonstrate the potential to improve the reliability of next-generation 3D NAND flash memory.

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“…The dramatic shift from the compute-centric paradigm to the data-centric paradigm in this era of big data has led to a surge in the flow of asynchronous data [1]- [2]. Ultra-dense storage technologies are urgently required to cope up with this data explosion [3].…”

Section: Introductionmentioning

confidence: 99%

“…were proposed [10]- [11]. 3D NAND flash memory has emerged as the most promising candidate for handling big data [2].…”

Section: Introductionmentioning

confidence: 99%

Analytical Modeling of 3D NAND Flash Cell With a Gaussian Doping Profile

Kumar

Sahay

2022

IEEE Access

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The incessantly increasing demand for highly dense storage medium in this era of big-data has led to the development of 3D NAND Flash memories. 3D NAND Flash based SSDs have revolutionized edge storage and become an integral part of the data warehouses and the cloud storage systems. The conventional 3D NAND flash memory with greater than hundred stacked word-line (WL) layers suffer from channel tapering and non-uniformity in the threshold voltage of cells in different WL layers which necessitates the use of different programming voltages for different WL layers and a complex error-correction circuitry. A non-uniform vertical (Gaussian) channel doping profile alleviates the threshold voltage non-uniformity and leads to a significant reduction in the complexity of the error-correction circuitry and a simple (uniform) programming scheme for all WLs. Although behavioral models have been proposed to utilize 3D NAND flash memory for circuit and system-level applications, an analytical model is important to understand the intricate details of the device physics and propose design guidelines for efficient cell design. To this end, in this paper, for the first time, we have proposed an analytical model for the characteristic length, surface potential and inner potential of the Macaroni-body 3D NAND flash cell with vertical Gaussian doping profile. A strong agreement between the analytical model and the TCAD simulations for different gate lengths (down to 25 nm), inner and outer radius, channel and oxide thickness of the 3D NAND flash cell validates the efficacy of the developed model.INDEX TERMS 3D NAND flash memory, Macaroni body, Vertical Gaussian doping, Analytical model.

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An Empirical Study of Quad-Level Cell (QLC) NAND Flash SSDs for Big Data Applications

Cited by 19 publications

References 7 publications

Wear leveling in SSDs considered harmful

Wear leveling in SSDs considered harmful

Effect of Noncircular Channel on Distribution of Threshold Voltage in 3D NAND Flash Memory

Analytical Modeling of 3D NAND Flash Cell With a Gaussian Doping Profile

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