SHF: Small: Characterizing and Optimizing 3D NAND Flash

在几乎所有具有国家重要性的应用领域都需要廉价、可靠和大容量的存储。例如，气候预测、核模拟和计算化学等应用程序需要操作大量的数据集。一种特殊类型的存储产品，称为NAND闪存，由于其性能，可靠性和功率效率优于传统磁盘驱动器，因此适合存储如此大的数据集，因此最近被广泛采用。然而，随着数据集规模的不断增加，市场上现有的传统NAND产品难以满足高性能和高可靠性的需求。3D NAND闪存是闪存世界中解决可扩展性问题的最新架构改进，它使闪存单元能够在多层中垂直堆叠。尽管3D NAND闪存前景光明，但从工作负载行为和资源利用的角度来看，其基本特征和内部结构至今尚未得到很好的理解。然而，架构、固件和系统软件级别的问题和潜在的机会在很大程度上被忽略了，这是本项目试图解决的问题。该项目的成果有望提高3D NAND存储在许多大数据应用领域的设计和利用。这个项目的教育和推广部分包括(1)一个关于先进存储系统概念的新的研究生水平课程；(2)邀请宾夕法尼亚州立大学Schreyer荣誉学院的本科生参与研究活动；(3)让宾夕法尼亚州立大学本科/研究生综合项目（IUG）的学生对这个主题感兴趣，以便在这个项目中进行研究生学习；(4)为高中女生和高中教师组织夏令营。具体而言，该项目对3D NAND闪存（特别是使用它们构建的固态设备）进行了深入研究，旨在确定3D NAND闪存的工作负载和资源利用特征，实施和评估一套针对3D NAND闪存架构以及2D/3D NAND闪存混合结构的架构、固件和系统软件级优化。该项目包括四项任务：(1)对3D NAND闪存的各种架构优化进行彻底探索；(2)研究固件级优化，如长读取延迟缓解，以及各种可靠性和生命周期增强技术；(3)深入研究文件系统级请求调度等系统软件级问题；(4)使用不同类型的应用程序工作负载和内部3D NAND模拟基础设施对优化进行详细的实验评估。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Inexpensive, reliable and large storage capacities are desirable in almost all application domains of national importance. For example, applications such as climate prediction, nuclear simulation and computational chemistry manipulate enormous datasets. A specific type of storage products, called NAND Flash, are suitable candidates for storing such large datasets given their performance, reliability and power efficiency advantages over traditional disk drives, and thus have seen widespread adoption recently. However, with continuous increase in dataset sizes, conventional NAND products available in the market are experiencing difficulty in coping with high performance and high reliability demands. 3D NAND flash is the newest architectural enhancement in the flash world to address this scalability problem, by enabling flash-memory cells to be stacked vertically in multiple layers. Despite the promise of 3D NAND flash, its fundamental characteristics and internal structures are not well understood as of today, from both the workload behavior and resource utilization perspectives. Yet architectural, firmware and system software level problems and potential opportunities have largely been ignored, which this project seeks to address. The outcome of this project is expected to enhance the design and utilization of 3D NAND storage in many big data application domains. The educational and outreach components of this project includes (1) a new graduate level course on advanced storage system concepts; (2) engaging undergraduates from Penn State's Schreyer Honors College in the research activities; (3) involving students from the Integrated Undergraduate/Graduate (IUG) program at Penn State to interest them in this topic, for possible graduate study in this project; and (4) organizing summer camps for high school girls and high school teachers.Specifically, this project conducts an in-depth study of 3D NAND flash memory (in particular solid state devices built using them), with the intent of identifying the workload and resource utilization characteristics of 3D NAND flash, implementing and evaluating a set of architectural, firmware and system software level optimizations targeting 3D NAND flash architectures as well as 2D/3D NAND flash hybrids. The project consists of four tasks: (1) performing a thorough exploration of various architectural optimizations specific to 3D NAND flash; (2) investigating firmware-level optimizations such as long read latency mitigation, as well as various reliability and lifetime enhancement techniques; (3) conducting an in-depth study of system software level issues such as file system-level request scheduling; and (4) performing a detailed experimental evaluation of the optimizations using different types of application workloads and an in-house 3D NAND simulation infrastructure.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.