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中，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处理巨大的数据集。一种名为NAND闪存的特定类型的存储产品适合存储如此大型的数据集，因为其性能、可靠性和能效优于传统磁盘驱动器，因此最近得到了广泛采用。然而，随着数据集规模的不断增加，市场上现有的传统NAND产品正面临着难以满足高性能和高可靠性的需求。3D NAND闪存是闪存领域解决这一可扩展性问题的最新架构增强，它使闪存单元能够垂直堆叠在多个层中。尽管3D NAND闪存前景看好，但从工作负载行为和资源利用率的角度来看，它的基本特征和内部结构到目前为止还没有得到很好的理解。然而，架构、固件和系统软件层面的问题和潜在机会在很大程度上被忽视了，这是本项目试图解决的问题。该项目的成果有望促进3D NAND存储在许多大数据应用领域的设计和使用。该项目的教育和推广部分包括：(1)关于高级存储系统概念的新研究生级别课程；(2)让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生/研究生(IUG)项目的学生对这一主题感兴趣，以便在该项目中可能进行研究生学习；具体而言，本项目对3D NAND闪存(尤其是使用3D NAND闪存构建的固态设备)进行深入研究，目的是确定3D NAND闪存的工作负载和资源利用特征，实施并评估一套针对3D NAND闪存架构以及2D/3D NAND闪存混合架构的架构、固件和系统软件级别的优化。该项目包括四个任务：(1)深入研究针对3D NAND Flash的各种体系结构优化；(2)研究固件级优化，如长读取延迟缓解，以及各种可靠性和寿命增强技术；(3)深入研究系统软件级问题，如文件系统级请求调度；以及(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NSF的法定使命，并通过使用基金会的智力优势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.