跨平台、多用户iSCSI存储系统的实现与管理

SCSI协议用来与I／O设备尤其是存储设备通信。iSCSI是工作在TCP／IP之上的SCSI传输协议,其基本功能是将SCSI命令封装在IP包内,通过TCP／IP网络传输到存储设备,再由网络接收命令处理的结果。本文将介绍iSCSI在Linux和Windows 2000两种操作系统下的实现过程,论述 iSCSI的多用户访问和管理方法,最后对所实现的iSCSI系统的性能测试结果进行分析。     

基于SCSI的故障注入工具设计与实现

研究海量存储系统的可用性评测,设计一种基于小型计算机系统接口(SCSI)协议的故障注入工具。该工具在SCSI协议中间层截获SCSI上层命令,修改命令后,能够实现多种暂态和永久故障的注入,有效地模拟存储系统可能遇到的各种故障。根据目标系统特点确定故障模型和注入参数,注入结束后,进行注入结果回收和离线数据分析。实验测试结果验证了该故障注入工具的有效性。     

保障连续媒体流用户层QoS 的缓存控制

研究了缓存控制对媒体流用户层QoS 的影响.多媒体系统信宿端通常采用播放缓存来补偿时延抖动,提高媒体流播放的连续性.缓存控制虽然能够降低时延抖动的影响,却增加了端到端时延.时延或时延抖动是用户可感知的QoS 参数,缓存控制对用户层QoS 的影响究竟如何呢?利用已有的应用层向用户层QoS 映射的研究结果,分析缓存控制参数与端到端QoS 参数、应用层QoS 参数的关系,获得了缓存控制参数与用户层QoS 参数的关系.从理论上深入挖掘缓存控制对用户层QoS 参数的作用,给出了提供确定时延和时延抖动保障的缓存容量值,论证了在网络环境一定时存在提供最佳用户层QoS 的缓存容量值.实验结果验证了分析.     

嵌入式虚拟磁带库驱动模块的设计

本文设计并实现了嵌入式虚拟磁带库(VTL)的SCSI控制器驱动模块,它完成数据传输、SCSI命令处理和任务管理等VTL的核心功能。系统测试表明,该模块设计可行、运行稳定,并对常用备份软件具有良好的兼容性。     

使用批量处理方法提高iSCSI存储系统性能的策略研究

iSCSI存储系统在IP网络上传输SCSI协议,但是在网络上大量的SCSI命令、状态以及小数据的传输严重影响了网络存储系统的性能.传统的批量处理方法将多个小的命令请求合并为一个大的请求,然而参数K的设定基于经验,缺少定量分析.通过排队理论建立SCSI命令批量处理的数学模型,然后在iSCSI存储协议结构中设计K-batch模块,最后应用网络仿真软件ns-2建立仿真场景对存储系统进行测试.随着命令到达率λ的变化,批量处理参数K作相应的实时调整.实验结果显示,该批量处理策略可明显降低命令的平均响应时间,提高iSCSI存储系统性能.     

iSCSI协议性能分析

iSCSI协议实现了通过IP网络存取SCSI设备.SCSI命令描述块被封装成iSCSI协议数据单元通过TCP/IP协议传送.iSCSI协议开销相对较大,iSCSI的性能受到网络最大传输单元和iSCSI协议参数的限制.     

基于缓存管理的网络编码中继传输方案

针对中继协作无线网络中节点缓存空间有限以及传输和缓存数据包都存在开销等问题进行了研究,提出了一种基于缓存管理的网络编码中继传输方案。在传输过程中该方案以最小化系统开销为目标,考虑多流综合优化问题,利用马尔可夫链对缓存队列进行建模分析。结合编码流速率增加编码机会,获得中继处不同流的缓存阈值,更合理地实现了编码决策。分析与仿真结果表明该方案能有效权衡编码机会和开销,相比其他方案能有效降低时延且提高网络吞吐量。     

iSCSI目标器的实现

SCSI是一种支持块级别访问的通用磁盘技术,但主要缺点是SCSI总线的距离限制.iSCSI协议使用以太网传输SCSI命令,因而可以有效地解决SCSI的扩展性.研究iSCSI的协议,并提出iSCSI目标器的实现模型.     

ISCSI协议的性能研究

ISCSI是基于IP的网络存储协议中最引人注目的技术之一,它将SCSI协议映射到TCP/IP协议上,使得SCSI命令和数据可以在传统的IP网络上传输,基于通用的IP网络是iSCSI最显著的优点.通过介绍iSCSI协议体系结构和功能实现流程,并对ISCSI协议进行仿真,在对仿真结果分析的基础上,得出结论ISCSI适合在高带宽网络环境下传输大量块数据,且网络带宽对ISCSI协议性能的影响会随着带宽的增加而减小.     

在Cache系统实现主流互联网直播服务

目前互联网直播采集端采用RTMP协议推流,服务端主流采用RTMP、HLS、HTTP-FLV 3种传输技术,其中又以HTrP-FLV为主占据70％以上的直播平台.系统性介绍了针对HTTP-FLV的视频传输协议,设计和实现了直播业务的缓存分发服务.     

Study of the performance impact of a cache buffer in solid-state disks

An SSD generally has a small memory, called cache buffer, to increase its performance and the frequently accessed data are maintained in this cache buffer. These cached data must periodically write back to the NAND Flash memory to prevent the data loss due to sudden power-off, and it should immediately flush all dirty data items into a non-volatile storage media (i.e., NAND Flash memory), when receiving a flush command, while the flush command is supported in Serial ATA (SATA) and Serial Attached SCSI (SAS). Thus, a flush command is an important factor to give significant impact on SSD performance.In this paper, we have investigated the impact of a flush command on SSD performance and have conducted in-depth experiments with versatile workloads, using the modified FlashSim simulator. Our performance measurements using PC and server workloads provide several interesting conclusions. First, a cache buffer without a flush command could improve SSD performance as a cache buffer size increases, since more requested data could be handled in the cache buffer. Second, our experiments have revealed that a flush command might give a negative impact on SSD performance. The average response time per request with a flush command is getting worse compared to not supporting the flush command, as cache buffer size increases. Finally, we have proposed the backend flushing scheme to nullify the negative performance impact of the flush command. The backend flushing scheme first writes the requested data into a cache buffer and sends the acknowledgment of the request completion to a host system. Then, it writes back the data in the cache buffer to NAND Flash memory. Thus, the proposed scheme could improve SSD performance since it might reduce the number of the dirty data items in a cache buffer to write back to NAND Flash memory.All these results suggest that a flush command could give a negative impact on SSD performance and our proposed backend flushing scheme could improve the SSD performance while supporting a flush command.     

基于SOPC的SCSI应用系统设计方法的研究

在分析了SCSI应用系统结构和常规设计方法的基础上，提出了一种基于可编程片上系统和处理器软核技术的SCSI应用系统的设计方案，其中应用系统控制核心选用了基于NIOS软核的微处理器，将SCSI控制单元的外部主机处理器，DMA数据通道控制和数据缓存控制逻辑等集成在1片FPGA上实现，在能充分利用逻辑器件资源的同时，使得设计更紧凑、灵活、高速和可靠，     

基于NIOS的SCSI应用系统设计

介绍一种基于可编程片上系统和处理器软核技术的SCSI应用系统的设计方案,其应用系统控制核心选用了基于NIOS软核的微处理器,将SCSI控制单元的外部主机处理器,DMA数据通道控制和数据缓存控制逻辑等集成在1片FPGA上实现,在能充分利用逻辑器件资源的同时,使得设计更紧凑、灵活、高速和可靠。     

基于SRP的IB-SAN设计与实现

介绍了基于SRP的IB-SAN的整体结构,分析了SCSI read/write命令处理过程中的两个关键问题,即数据缓冲区的内存注册/注销方法和RDMA操作的执行者获取对方数据缓冲区信息的方式。实验结果表明,SRP能够使InfiniBand网络性能得到充分发挥,系统的总体I/O性能明显优于基于iSCSI协议的IB-SAN。     

一种SCSI目标器设计与评估

SCSI目标器是磁盘阵列控制器软件中的关键组成部分之一;设计并实现了一种SCSI目标器,详细描述了SCSI目标器的功能及其内部体系结构,阐述了目标器对读写请求的不同处理流程;该SCSI目标器是可配置的,它既能够辅助磁盘阵列控制器软件系统开发,也能够胜任磁盘阵列控制器SCSI目标器的功能;为了验证该SCSI目标器的性能,采用相关评测工具对其有负载和无负载两种情况的读写性能进行了评测,测试结果表明该SCSI目标器的实际性能达到了预期的设计目标。     

Deconstructing on-board disk cache by using block-level real traces

On-board disk cache is an effective approach to improve disk performance by reducing the number of physical accesses to the magnetic media. Disk drive manufacturers are increasing the on-board disk cache size to match the capacity growth of the backend magnetic media. Some disk drives nowadays have a cache of 32 MB. Modern computer systems use large amounts of memory to improve performance, any data brought into host memory will be re-accessed there, not in the on-board disk cache. This feature has a significant impact on the behavior of disk cache. This is because computer systems are complex systems consisting of various components. The components are correlated with each other. Therefore, a specific component cannot be isolated from the overall system when we analyze its performance behavior. This paper employs four block-level real traces to explore the performance behavior of the on-board disk cache by considering the impacts of the cache hierarchy contained in computer systems. The analysis gives three major implications: (1) I/O stream at block-level contains negligible temporal locality. Therefore, read/write cache can only achieve marginal benefits. (2) Static write cache does not achieve performance gains since the write stream does not have too much interference with the read stream. Therefore, it is better to leave the on-board disk cache shared by both the write and read streams. (3) Read cache dominates the contribution to the hit ratio besides prefetch. Thus, it is better to focus on improving the read performance rather than write performance of disk cache.     

The cache assignment problem and its application to database buffermanagement

Given N request streams and L⩽N LRU caches, the cache assignment problem asks to which cache each stream should be assigned in order to minimize the overall miss rate. An efficient solution to this problem is provided, based on characterizing each stream using the stack reference model and characterizing the interaction of the streams using a bursty stream model. It is shown that for Bernoulli (purely random) mixing of streams, the optimal cache assignment is to have one cache per stream. In practice streams are mixed in a way that is much “burstier” than can be represented by the Bernoulli model. Therefore a method is presented for superposition of bursty streams. The performance of the methods developed for bursty stream superposition and cache assignment are tested using trace data obtained from the database system DB2. The resulting cache assignment recommendations are then applied to the DB2 system, and considerable performance improvement is found to result     

基于IP的全局网络存储解决方法

1.引言随着Internet的应用和普及,信息爆炸性地增长。因此,改善存储性能和提供7×24的可用性的压力也越来越大。传统的存储技术(BAS)采用并行SCSI或DAS技术,基于总线结构,无法提供足够灵活和可扩展的功能以满足如今对应用和存储快速布署的要求。