YAFFS嵌入式文件系统应用研究

本文介绍了NAND闪存设备的特点和针对NAND闪存设计的YAFFS（Yet Another Flash File System）嵌入式文件系统,并且详细探讨了在ARM处理器3SC2410和嵌入式Linux平台上建立基于NAND闪存的YAFFS根文件系统的方法步骤,同时给出了详细的代码。     

YAFFS嵌入式文件系统应用研究

本文介绍了NAND闪存设备的特点和针对NAND闪存设计的YAFFS(YetAnotherFlashFileSystem)嵌入式文件系统,并且详细探讨了在ARM处理器3SC2410和嵌入式Linux平台上建立基于NAND闪存的YAFFS根文件系统的方法步骤,同时给出了详细的代码。     

Linux内核与内存关系的几个问题的探讨

Linux内核与内存之间的关系涉及内核中与系统硬件相关的部分，本文作者在阅读Linux内核源代码的基础上，探讨内核与内存之间关系的若干基本问题的答案，这些问题包括：内核与进程的关系、内核映象的生成、系统启动过程中内核与内在的关系、内核堆栈的机制等，本文的讨论基于Intel的80x86平台上的内核2．2。     

一种基于NAND闪存的嵌入式Linux文件系统

本文分析了NAND闪存的独特属性和它对嵌入式Linux文件系统提出的新要求，在此基础上提出了一个基于NAND闪存的嵌入式Linux文件系统。     

非易失存储器NAND Flash及其在嵌入式系统中的应用

文中介绍了NAND Flash的芯片内部组织结构、主要的外部引脚及其功能、NAND Flash的类型、NAND Flash所支持的文件系统、与微处理器的连接和NAND Flash的固有特性，并对比了NAND和NAND Flash的异同。最后简述了闪存固件程序架构和如何在Linux操作系统中加入对NAND Flash的支持。     

未来存储谁主天下？

近年来NAND型闪存在存储容量上的飞速发展，吸引了众多关注的目光，其能否取代硬盘成为未来主要的存储手段已在业务引起广泛争论。为此，本文在简要阐述NAND型闪存基本原理和结构的基础上，从速度，容量，价格，使用寿命等方面，与硬盘的性能进行对比分析，以期让更多的人了解NAND型闪存……[编者按]     

NAND闪存存储文件系统

NAND闪存已经成为便携式设备的主要存储介质。由于闪存自身的物理特性,需要在现有文件系统层与闪存的存储物理层之间引入闪存转换层。但是,现有文件系统主要针对磁盘存储系统设计的,没有考虑NAND闪存物理特性。这种方法效率低、影响便携式设备的性能。本文概述了NAND闪存的存储文件系统,分析比较了其中三种主要文件系统,为基于NAND闪存存储介质的便携式系统设计提供了参考意见。     

嵌入式系统中MLC闪存驱动研究

MLC闪存高密度、低成本的特点,适于做海量存储器.文中以在WinCE6.0平台下实现高性能的MLC闪存驱动为目的,介绍了ARM嵌入式系统中NAND FLASH控制器的工作原理;讨论了WinCE下闪存驱动可采用的两种架构,并在新的MDD、PDD闪存驱动架构下实现了该驱动;介绍并实现了双片操作命令操作;介绍了DMA的工作原理,并实现了DMA编程.测试表明,较之前传统架构及传统操作命令,写入速度提高1.8倍.读出速度提高1.3倍,可靠性也大幅提高.该设计方案可放应用于需要大容量存储的嵌入式系统中.     

非易失存储器NAND Flash及其在嵌入式系统中的应用

文中介绍了NAND Flash的芯片内部组织结构、主要的外部引脚及其功能、NAND Flash的类型、NAND Flash所支持的文件系统、与微处理器的连接和NAND Flash的固有特性,并对比了NAND和NOR Flash的异同。最后简述了闪存固件程序架构和如何在Linux操作系统中加入对NAND Flash的支持。     

闪存设备在嵌入式Linux系统中的应用

论述了多种闪存设备在嵌入式Linux系统应用过程中的关键问题的解决方法。分析了内核对不同闪存的支持和相关代码，给出了文件系统的设计和使用方法。对嵌入式系统存储设备的设计具有借鉴意义。     

基于PXA3xx处理器的NAND闪存DMA方案

针对PXA3xx处理器的特性,提出一种DMA控制器系统架构方案,并在此架构上结合嵌入式Linux操作系统实现NAND Flash的底层驱动程序.重点设计了基于JFFS2文件系统的读操作测试方案,测试结果表明,DMA方式能够有效降低CPU处理负载,缓解NAND Flash性能瓶颈.     

嵌入式Linux中闪存设备驱动程序开发

嵌入式系统通常使用闪存作为存储设备，嵌入式Linux下的MTD技术可以方便地访问Flash这样的MTD设备。文章介绍了Linux块设备驱动程序框架，详细分析了MTD设备驱动程序层次结构、核心功能模块和数据结构，最后以Motorola MPC860T开发板为例，系统地给出了针对特定Flash的MTD驱动程序开发实例。     

基于NAND型闪存的嵌入式文件系统设计

由于具有高密度和良好的存取速率等特点,NAND型闪存在嵌入式系统领域中被广泛应用,但其所固有的擦除－写入更新机制以及高坏块率等特性却又成为其在应用中的障碍。提出了一种基于NAND型闪存的日志结构嵌入式文件系统,用于充分利用NAND型闪存的优势并克服其缺陷。文件系统在嵌入式Linux操作系统中予以实现,并进行了性能测试。     

A high performance NAND array file system based on multiple NAND flash memories

The existing NAND flash memory file systems have not taken into account multiple NAND flash memories for large-capacity storage. In addition, since large-capacity NAND flash memory is much more expensive than the same capacity hard disk drive, it is cost wise infeasible to build large-capacity flash drives. To resolve these problems, this paper suggests a new file system called NAFS for large-capacity storage with multiple small-capacity and low-cost NAND flash memories. It adopts a new cache policy, mount scheme, and garbage collection scheme in order to improve read and write performance, to reduce the mount time, and to improve the wear-leveling effectiveness. Our performance results show that NAFS is more suitable for large-capacity storage than conventional NAND file systems such as YAFFS2 and JFFS2 and a disk-based file system for Linux such as HDD-RAID5-EXT3 in terms of the read and write transfer rate using a double cache policy and the mount time using metadata stored on a separate partition. We also demonstrate that the wear-leveling effectiveness of NAFS can be improved by our adaptive garbage collection scheme.     

SA-YAFFS:支持交换系统的YAFFS闪存文件系统

LINUX交换系统不支持在闪存（NAND flash）上直接建立交换区域。虽然可以使用NFTL／FTL层或者FASS闪存交换系统实现在闪存上建立交换分区。然而,这两种方法都采用静态分配交换区域,将交换系统的读写磨损限制在了闪存固定的某个区域,可能会造成闪存局部过度磨损。提出的SA-YAFFS系统,将交换系统的支持性和闪存文件系统有机统一,在闪存上动态分配交换区域,避免了将交换系统的读写磨损限制在闪存固定的区域,并利用文件系统中大量的空闲空间分担交换系统带来的磨损,避免了局部过度磨损。实验表明,当“文件系统逻辑配额的剩余空闲空间＋交换系统逻辑配额”增加到n倍,交换系统导致的磨损为原来的1／n。     

A user-visible solid-state storage system with software-defined fusion methods for PCM and NAND flash

Existing SSD technology exploits the properties of NAND flash and leverages NAND flash with a controller running FTL algorithms to improve system performance. On one hand, however, in this black-box-modeled structure, data semantic information is hard to be transferred and interpreted by conventional interfaces. Hence, SSD firmware fails to make full use of the performance potential of SSD by utilizing semantic information. Moreover, the host cannot obtain physical characteristics and statistical information about SSD, failing to be used by the file system or I/O scheduling algorithm designed for the disks. On the other hand, in SSD-based storage systems, persistent data are stored in the NAND flash and however manipulated in DRAM, causing the decoupled inefficiency. The data being closer to the processors are much easier to be lost due to the volatile property of DRAM, leading to serious data reliability problems. What’s more, restrictive read/program granularity and out-of-place updates limit the performance while flash suffers from small size operations.In order to address these problems, we propose a user-visible solid-state storage system with software-defined fusion methods for PCM and NAND flash. PCM is used for improving data reliability and reducing the write amplification of NAND flash as PCM shows some outstanding features, such as in-place updates, byte-addressable, non-volatile properties and better endurance. In this system, we manage the storage device as user-visible structure rather than black-box-modeled structure. In detail, we expose the number of channels, erase counts and data distribution of PCM/NAND flash to the host and design FTL algorithm closer to file system to obtain more semantic information of data accessing. PCM can be software-defined as the same level storage or buffer of NAND flash to reduce the WA (Write Amplification) of NAND flash and improve the data reliability. Moreover, some key software components (such as FTL, I/O scheduling and buffer management) are also reconfigurable and operated easily combined with physical characteristics. To achieve these design goals, we implement a Host Fusion Storage Layer (HFSL) and redesign the lengthy I/O path. Applications or filesystem can access PCM/flash directly via provided interfaces by HFSL without passing traditional I/O subsystem. Moreover, we provide the system management software to make the storage system can be easily software-defined by the upper-level system. We implement our software-defined fusion storage system in our actual hardware prototype and extensive experimental results demonstrate the efficiency of the proposed schemes.     

基于NAND Flash的嵌入式数据库索引机制的改进

目前嵌入式系统设计中, NAND Flash和数据库的使用越来越频繁.在实际系统中,NAND Flash存储设备品种繁多,此外,数据库的存储效率还取决于应用环境中的工作负载.以Berkeley DB为原型进行改进,加入了BFTL层和动态调整机制以适应不同的设备环境和工作负载.在两种工作负载和三种设备环境中,根据改进后的数据库性能分析,得出该改进能适应各种工作负载和设备环境.