基于闪存设备分区的新型虚拟EEPROM设备的设计与研究

针对当前嵌入式系统对于低成本迫切需求,研究并设计了一种基于闪存设备（NAND FLASH）的新型虚拟EEPROM（Virtual EEPROM）设备。该设备被虚拟为操作系统NAND设备分区使用,使用数据备份机制确保数据信息安全性。针对NAND只支持页面单元的编程操作,使用缓冲区日志更新的方法,高效地解决Virtual EEPROM字节编程问题。最后通过设计损益均衡层实现NAND存储块的统一管理,对坏块和寿命问题进行大幅优化。分析结果表明,Virtual EEPROM具备NAND快速编程特性,擦写寿命较EEPROM有很大优势。该设计架构具备很好的系统兼容性,可以扩展移植于多种嵌入式平台。     

基于FPGA的NAND Flash控制接口电路设计

本文在比较NAND Flash的优、缺点,分析控制接口电路的功能特性的基础上,论述了主控器的设计实现方法,通过写控制字的方式将复杂的NAND Flash接口映射为简单的SRAM接口。并根据ECC算法原理,阐述了ECC校验码生成、查错与纠错的实现方法。本文设计的NAND Flash控制接口电路的操作指令在Xilinx的Spartan-3Board上得到了功能验证,工作频率达到100MHz。     

NAND FLASH编程实现研究分析

以阐明编程支持NAND FLASH的方法为目的。总览了NAND FLASH层次结构;讨论了NAND FLASH的写操作过程,这种写操作的特点也是FLASH有别于其它存储介质的地方,同时也对NAND FLASH的擦除操作做了介绍;在对整体的框架和特点有了了解之后,进一步对编程支持NAND FLASH的过程中会遇到的一些概念和细节给出了具体的说明。对NAND FLASH的编程支持有一定的复杂性,但只要了解了它的工作方式,也并非难事。     

NAND Flash文件系统方案及其可靠性设计

NAND Flash具有高存储密度和高存储速率的特点,在嵌入式系统领域得到了广泛应用,如何使其文件系统的性能最优化成为本文讨论的主题.本文首先提出文件系统的设计方法,主要阐述面向嵌入式应用的FAT文件系统;接着,针对NAND开ash存在固有的坏块这一弱点,为了提高整个系统的可靠性,提出一种利用嵌入式文件系统进行坏块处理的策略,核心思想为利用Flash存储器上未使用空间来代替坏块,同时,在FAT表中标记出损坏的坏的信息,避免以后对坏块进行读写.本策略经项目的具体应用证明,具有较高可靠性.     

NAND Flash内存设备的读写控制设计

针对NAND Flash闪存设备在嵌入式系统中的应用,详细分析了Flash闪存设备的接口设计方法。根据NANDFlash的读写特性,采用Hynix半导体公司的Flash H27U1G8F2B,设计一种闪存数据读写控制方法和驱动流程。该方法能够应用于各种NAND Flash的读写控制,具有良好的程序结构和较高的代码运行效率。     

基于地址映射的NAND Flash控制器设计

针对嵌入式数据采集系统对NAND Flash进行读写控制时出现的坏块问题和磨损失衡问题,对数据采集系统的工作特点进行分析,借鉴闪存转换层的思想,提出了一种基于地址映射的NAND Flash控制方法,通过建立、维护、查询NAND Flash存储块逻辑地址与物理地址之间的映射关系表,实现NAND Flash的坏块管理和磨损均衡功能,同时介绍了使用地址映射方法的NAND Flash控制器设计过程;仿真测试和实际应用结果表明,基于地址映射方法设计的NAND Flash控制器能够识别、管理出厂坏块和突发坏块,均衡存储块的磨损,提高嵌入式数据采集系统的可靠性;该方法实现过程简单,无需移植文件系统,硬件资源要求低,为嵌入式数据采集系统中NAND Flash的读写控制提供了新的思路。     

基于权重堆排序的NAND Flash静态磨损均衡机制

磨损均衡机制作为闪存转换层的基础机制之一,其主要功能是延长闪存块使用寿命和提高存储数据的可靠性。现有的磨损均衡机制着重于减少闪存块的擦除次数,忽略了在磨损均衡操作过程中选择擦除脏块的不合理所带来的不必要数据迁移开销,从而影响了固态硬盘的整体读写性能。针对该问题,提出了一种基于权重堆排序的 NAND Flash静态磨损均衡机制WHWL。首先,提出一种基于页数据访问频率和块擦除次数的权重的热度计算方法,有效地提高擦除次数少（冷块）且数据访问频率低（冷数据）的目标块命中率,避免了多余的数据迁移操作;其次,提出了一种基于权重的堆排序目标块选择算法,以加快目标块的筛选。实验结果表明,与现有的PWL和BET算法相比,在使用相同映射机制的条件下,WHWL能够分别提升固态硬盘寿命1.28、5.83倍,数据迁移次数也有明显的降低。     

NAND Flash坏块管理研究

在当今数字技术飞速发展的时代,NAND Flash因其非易失性及可擦除性而在数码相机和固态MPEG-4摄像机图像存储及电子硬盘应用方面需求越来越大,也已广泛应用于诸如Appie iPod Nano和SanDisk Sansa等最新媒体播放器的音乐和视频存储.我们主要研究了NANDFlash中坏块出现的原因,对坏块进行了分类,并且提出了相应的管理方案.     

Android存储系统中NAND闪存性能的改进

针对Android存储系统在闪存管理上存在较差的磨损均衡效果和较高的垃圾回收额外开销的缺陷,引入冷热数据分离策略,将文件按照不同热度写入对应热度的物理存储单元,同时改进垃圾回收策略,以达到良好的磨损均衡效果并减少垃圾回收额外开销。基于Android平台的实验结果表明,改进后的策略在有效减少NAND闪存垃圾回收额外开销的同时,还能有效改善其磨损均衡效果。     

NAND Flash的坏块管理设计

主要介绍了基于嵌入式Linux的NAND Flash坏块管理设计和实现方案,详细阐述了坏块映射表的建立、维护及其相关算法,同时分析了此坏块算法在Linux内核及Bootloader中的具体应用。测试结果表明该算法能够处理NANDFlash的相关坏块问题,具有较高的稳定性。     

嵌入式设备NAND Flash存储系统的设计与实现

为了实现一种嵌入式设备存储系统的解决方案,对嵌入式设备广泛采用的大容量存储设备NAND Flash进行了深入的研究.设计了一种嵌入式设备中NAND Flash存储系统的解决方案,介绍了其功能用途和系统结构,分层介绍了系统的具体设计,重点介绍了比较独特的块设备驱动层和FTL层的设计方法以及对驱动初始化的优化.通过实际设计NAND Flash存储系统Linux驱动,说明了该系统设计实际应用时的出色效果.     

Real-time emulation and analysis of multiple NAND flash channels in solid-state storage device

NAND Flash is the most prevalent memory technology used today in data storage systems covering a wide range of applications, from consumer devices to high-end enterprise systems. In this work, we present a modular and versatile FPGA-based platform that achieves accurate emulation of multiple NAND Flash channels. The NAND Flash emulator is based on an expandable and reconfigurable architecture that can be used for developing and testing new NAND Flash controllers and for analysing the behaviour of existing NAND Flash controllers and/or host device drivers. The presented NAND Flash emulator is based on PCIe-based FPGA boards attached to a high-end server, supports standard memory interfaces, responds to all memory commands in proper time and has the capability to emulate memory space in the range of a few TBs. The NAND Flash emulator has been prototyped and tested, and experimental results demonstrate that all timing requirements are satisfied under maximum read/write workloads. The NAND Flash emulator also includes a hardware tracer unit that records information of all commands exchanged at the NAND Flash interfaces along with high resolution timestamps. The recorded information can be used to analyse higher level functions, like wear leveling and garbage collection, and combined with other software tools for analysing cognitive functions. Experimental results demonstrate the advantage of using this emulator for analysing how host device drivers implement wear leveling and garbage collection functions.     

高密度存储服务器热设计

云计算和大数据时代对高密度存储服务器的需求越来越大。由于温度对电子元器件的性能和寿命有很大的影响,而高密度存储服务器的功率密度更大,故必须对其进行合理的热设计,以确保服务器工作时的温度在合理可控范围内。介绍了高密度存储服务器的结构,以及散热风道、散热器、风扇等关键散热部件的热设计方法。热设计整体方案采用吸风式的强迫风冷散热方式;基于Flotherm热仿真软件对整机系统进行了仿真优化;在35℃实际应用环境下对产品样机进行了热测试。测试结果表明,该热设计方案满足热设计要求。     

星载同步NAND FLASH存储控制器设计

为满足海量空间科学数据对高速存储的需求,设计一种星载同步NAND FLASH存储控制器.通过对星载存储系统吞吐率影响因素的分析,提出采用具有同步数据接口的NAND FLASH存储器件、在存储阵列之间引入八级流水操作、对NAND FLASH数据总线进行并行扩展的设计方案,对存储控制器的软硬件进行设计.实验结果表明,该设计能够有效提升星载存储系统的吞吐率,设计中的功能模块化及接口标准化有利于系统进一步灵活扩展.     

提高可移动存储设备管理系统安全运行的方案

可移动存储设备管理系统在运行时会面临攻击者采用任务管理器或第三方工具强行关闭的攻击,可能导致应用程序无法正常运行。为解决这类应用程序安全运行的问题,提出一种融合进程隐藏和进程守护技术的可移动存储设备管理系统安全运行方案。该方案利用改进的远程线程注入技术提高系统隐蔽性,利用双守护进程的两级监控体系提高系统健壮性,从而达到维护程序安全运行的目的。应用结果表明,该方案能够很好地抵抗强行关闭攻击。     

A multi-channel architecture for high-performance NAND flash-based storage system

Many mobile devices demand a large-capacity and high-performance storage system in order to store, retrieve, and process large multimedia data quickly. In this paper, we present a high-performance NAND flash-based storage system based on a multi-channel architecture. The proposed system consists of multiple independent channels, where each channel has multiple NAND flash memory chips. On this hardware, we investigate three optimization techniques to exploit I/O parallelism: striping, interleaving, and pipelining. By combining all the optimization techniques carefully, our system has shown 3.6 times higher overall performance compared to the conventional single-channel architecture.     

新的设备查找及散列网形成协议

基于对BlueMesh协议、BlueTree协议等多种协议的分析,介绍一种新的方法来解决蓝牙标准中设备查找和散列网形成的问题。在此基础上发展形成一种新的多跳蓝牙设备查找及散列网形成协议。新的协议可以基于非常简单的本地规则就能产生高概率连通性的拓扑。通过仿真表明它的方法实现简单、快速、低开销,对照目前已有的方案有更优的性能。     

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.     

基于NAND FLASH的大容量视频存储系统的设计

针对MPEG4格式压缩的视频数据,给出了采用NAND FLASH为存储介质,以FPGA为存储阵列的控制器,并用DSP作为数据处理的核心单元,来完成大容量视频数据存储的系统设计方法,同时对坏块的检测处理等关键问题提出了解决方案。     

Virtual duplication and mapping prefetching for emerging storage primitives in NAND flash memory storage systems

NAND flash memory has become the mainstream storage medium for both enterprise high performance computers and embedded systems. However, over the past several decades, the storage primitives that access secondary storage have remained unchanged, forcing NAND flash memory to serve merely as a block device like hard disk drive. Recently, several emerging storage primitives have been presented to explore the potential value of non-volatile memory devices. Although these primitives can significantly boost the access performance by providing virtual to logical address mappings, they still suffer from large RAM footprint to maintain the address mapping table and require further support for update operations.This paper presents ESP to optimize E merging S torage P rimitives with virtualization for flash memory storage systems. We propose two optimization strategies, virtual duplication and mapping prefetching to solve the critical issues in existing emerging storage primitives. The objective is to reduce unnecessary flash memory accesses and keep RAM footprint of address mapping table well under control. We have evaluated ESP on an embedded development platform. Experimental results show that ESP can significantly improve the write/read performance and reduce over 30% of garbage collection operations.