用双目标加权遗传算法解决网络磁盘阵列系统下校验散布布局优化问题的研究

廉价磁盘冗余阵列(RAID)作为一种提高存储系统可靠性和性能的技术,已经得到了广泛的应用,有关磁盘阵列结构和数据布局的研究也一直很活跃,但有关网络磁盘阵列下的数据布局的研究还不太多。本文首先概述了校验散布布局的技术和遗传算法的相关知识,提出了利用双目标加权遗传算法的思想解决网络磁盘阵列系统校验散布布局优化的问题。然后以“重构负截均匀分布”和“校验均匀分布”为双目标,使用改变的NSGA来解决网络磁盘阵列系统下校验散布布局的优化问题。最后给出了实验结果。     

神威3000A高可用海量存储系统

神威3000A海量存储系统采用基于文件分条的网络数据冗余方法,支持网络RAID1和RAID5冗余模式,能够对存储服务器及盘阵故障在线容错,是一个高可用的分布式存储系统。     

高可靠计算机系统的容错技术

高可靠性是计算机系统所要解决和实现的重要目标，而容错技术是提高可靠性的有效途径。章论述了可靠性的基本概念和3种故障模式；介绍了计算机容错设计所采用的硬件冗余、信息冗余和时间冗余技术，着重分析了RAID技术和纠错码技术；指出了计算机容错设计的发展趋势及面临的挑战。     

MegaDrive公司RAID系统精品展示

RAID是Redundant Array of Inexpensive Disks的缩写,按文译义是廉价冗余磁盘阵列,一般就称为磁盘阵列。它的原意是把若干相对便宜的驱动器组合起来成为逻辑上单独的驱动器,以便获得容错数据冗余的能力,恢复由于驱动器故障而可能会丢失的数据,而且价格与相当容量的硬盘机相比还要便宜些。 RAID系统的基本元部件包括2个或更多的驱动器和RAID软件。大多数RAID系统还包括1个或更多的SCSI卡,用于提高Mac机内置SCSI端口的性能。RAID 3和5系统通常适用于服务器,并往往装有     

高可靠计算机系统的容错技术

高可靠性是计算机系统所要解决和实现的重要目标,而容错技术是提高可靠性的有效途径.文章论述了可靠性的基本概念和3种故障模式;介绍了计算机容错设计所采用的硬件冗余、信息冗余和时间冗余技术,着重分析了RAID技术和纠错码技术;指出了计算机容错设计的发展趋势及面临的挑战.     

异构磁盘阵列RAID5结构数据布局研究

由于应用需求的快速发展以及网络存储系统的出现,因此异构磁盘阵列的变得越来越常见。RAID5由于较高的性能和可靠性以及较低的代价,是应用最为广泛的RAID结构。目前对异构磁盘阵列RAID5结构的研究,重点主要放在充分利磁盘存储空间以及对性能的定性研究。论文提出了一种异构磁盘阵列RAID5结构数据布局优化方法,该方法充分考虑异构磁盘的相对容量和性能,以及校验单元的散布对RAID5小数据写性能的影响,可以生成负载均匀分布或接近均匀分布的布局。仿真实验结果表明,对于多用户小数据访问模式,优化布局的性能明显优于简单RAID5布局,且具有更高的伸缩性。     

主动容错云存储系统的可靠性评价模型

除了传统的冗余机制,主动容错技术也被用来提高存储系统的可靠性。然而,当前对主动容错云存储系统可靠性的研究工作很少,而且都局限于硬盘故障服从指数分布的假设前提。针对主动容错磁盘冗余阵列RAID-5和RAID-6云存储系统提出两个可靠性状态转移模型,并基于转移模型设计了蒙特卡洛仿真算法,评价系统在一定运行周期内发生数据丢失事件的期望个数。该算法采用韦布分布函数模拟随时间变化（降低、恒定不变、或升高）的硬盘故障率,准确评价了主动容错机制、硬盘整体故障、故障修复、潜在块故障以及磁盘清洗过程对系统可靠性的影响。所提方法可以帮助系统设计者评估不同容错机制和系统参数对云存储系统可靠性的影响,有助于创建高可靠存储系统。     

基于奇偶校验的三容错数据布局研究

基于单容错编码的数据布局已经不能满足存储系统对可靠性越来越高的要求。对基于多容错编码的数据布局的研究受到了广泛的关注,并且出现了一些三容错的布局算法,如HDD1,HDD2等。但这些布局算法普遍存在冗余度较差、计算负载大等缺点。提出了一种基于三重奇偶校验的多容错数据布局算法TP-RAID(Triple Parity RAID)。该算法只需要在RAID5阵列系统中增加两个校验磁盘,通过水平、正向对角和反向对角三重奇偶校验,可容许同时发生的三个磁盘故障。该算法编码、解码简单,三重校验条纹长度相等,计算负载小,易于实现。此外,由于该算法中尽量减少了三重校验之间逻辑关联,使得该算法的小写性能比其他的三容错算法相比有了大幅度的提高。     

RAID技术落户台式机

RAID(Redundant Array of ldependent Disk,冗余独立磁盘阵列)是为提高性能和可靠性将数据和用于纠错的信息分别存放于两个或多个硬盘驱动器的一种数据存储方式。磁盘阵列由阵列管理软件和控制纠错的磁盘控制器管理。RAID技术通常用于网络服务器。 传统上,采用RAID技术的产品都比较昂贵。但是,随着计算机技术的普及,一些台式机(包括个人计算机和小型服务器)的用户也需要在他们的机器上运用RAID技术。     

基于多模块的可配置阵列存储系统的模拟实现

给出一个基于多模块的可配置磁盘阵列存储系统的框架设计与编程实现,软件支持RAID0、RAID1、RAID3、RAID5、RAID6等主流阵列级别,另外还添加了RAID5x阵列.采用多线程技术,能较真实地模拟客户与存储系统的动态交互过程,能根据用户的配置进行阵列正常、降级的读写性能测试.经实验验证,该软件能对阵列存储系统进行较为真实的模拟,进一步优化后,其可以作为磁盘阵列的性能、可靠性以及阵列优化方法的一个模拟研究平台.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.