基于Swift的副本数据自适应备份策略研究

冗余数据备份是保证云数据中心下数据可靠性的重要保障机制之一,OpenStack是一种开源的云计算IaaS层私有云服务搭建平台,目前已经在行业界广泛应用。OpenStack的Swift模块使用一致性哈希算法,采用Ring环选取副本备份节点的方式来完成负载均衡和数据备份。本文通过对Swift的实现机理和代码进行分析研究,指出其在副本放置节点选取上的不足,并进而提出优化选取策略ABS（Adaptive Backup Strategy）。该机制在实时监控当前存储节点的负载情况基础之上,根据预先设定的阈值上、下限,自适应选取最近可用的节点完成备份,以优化整体备份效率。通过与现有副本备份策略进行对比和实验验证表明,ABS在保持数据副本分配均衡性的基础之上,将系统存储的4种读写性能分别提高了3.4%~9.1%,达到了优化存取的目的。     

基于Areca Backup和云存储的开源免费备份策略

介绍一种基于开源备份软件Areca Backup和云存储的数据备份策略。该策略充分利用云存储技术实现备份数据的低成本和高可靠性存储。Areca Backup的数据加密功能使备份文件的云存储容易符合公司的安全规定。操作简易,适用于可靠性要求一般的数据备份。     

基于AHP-RBF的Swift云存储负载预测

通过对Swift云存储中Proxy Node的负载因素研究,提出结合层次分析法（AHP）和混合递阶遗传训练的RBF神经网络实现对Swift云存储负载情况的预测,其中使用AHP构造对云存储系统的负载层次化模式,提高负载预测的综合精度,设计了RBF神经网络预测模型,用混合递阶遗传算法（HHGA）确定RBF神经网络的参数和结构。仿真实验结果表明,对Swift云存储负载的预测具有可行性,能为系统动态负载均衡决策提供依据。     

基于固态硬盘的云存储分布式缓存策略

为满足海量数据存储的需求,提出一种基于低功耗、高性能固态硬盘的云存储系统分布式缓存策略.该策略对不同存储介质的硬盘虚拟化,将热点访问数据的缓存与存储相结合,实现在不同存储介质之间的热点数据迁移,解决热点元数据的访问一致性与存储服务器的动态负载均衡问题.工作负载压力测试结果表明,该策略可使云存储系统的读峰值速率最高提升约86％,并且能提高存储服务器的吞吐量.     

云存储环境下副本选择策略研究

云存储服务提供商为了满足各类云用户的存储需求,一般采用划分固定大小的数据块、冗余备份等技术来存储数据,关于块放置、最佳副本选择、副本粒度等存储机制的研究一直是加快大文件存取速度的重要内容。面向云存储系统中存储节点的异构性,设计了一种采用层次分析法对节点性能指标加权并依据加权指标改进粒子群算法的策略(AHPPSO)。通过引入与存储节点性能相关的加权评价矩阵,使得粒子群算法向综合性能较高的节点进化,在不增加存储空间成本的基础上,加快了存取数据的速度。在自主搭建的云存储系统中实现了该策略,实验结果显示该策略能够适应多种用户需求,并且在一定程度上实现系统负载均衡。     

Ceph分布式系统的ISCSI高可用集群

在分布式存储集群环境中,为了兼容现有存储协议,提高集群可扩展性,通常都会支持ISCSI存储协议.而现有ISCSI服务的高可用主要通过主从备份的方式实现,该方式会导致资源利用不充分,容易造成单节点负载过重等情况.本文基于Ceph分布式存储系统的优势,采用raft一致性算法等设计并实现ISCSI高可用集群.ISCSI集群使用自定义的节点选择策略实现服务负载均衡,并通过raft分布式协议实现服务故障迁移.实验表明,本文提出的方案是有效的,能够实现服务故障迁移,保证集群负载均衡.     

OpenStack Swift关键技术分析与性能评测

Swift是开源云平台管理项目OpenStack的对象存储系统,能够提供海量、可弹性扩展、低成本的云存储服务。首先对Swift的使用场景做了简要分析,然后针对Swift采用的一致性哈希、高可用服务等关键技术进行了详细分析,最后对Swift进行了性能评测。     

基于OpenStack的云存储系统的大文件存储方案

为解决开源云平台OpenStack的对象存储服务Swift在存储GB级大文件方面的不足,提出基于文件分割、片段合并、并行处理的GB级大文件的存储方案。分析Swift体系结构及其特点,在此基础上构建云存储系统的层次架构;制定GB级大文件的存储策略,设计关键数据结构和上传下载的核心流程,使用Java多线程实现该方案。部署云存储实验环境,通过实验验证了该方案的可行性,该方案突破了Swift对文件大小的限制,提高了文件的上传和下载速度。     

Swift云存储环境下基于I/O的负载均衡算法

开源云计算平台Openstack的云存储服务使用普通硬件构建的服务器集群为PB级别数据提供冗余的、高可靠的、可拓展的数据存储。针对集群中一部分节点访问过热而另一部分节点资源利用不充分的情况,对核心模块Swift中最重要的组件Ring中用到的一致性哈希算法进行改进。实验结果表明,该算法能在最大程度兼顾负载均衡的同时提高存储资源的利用率,既考虑了集群中各节点的处理能力,同时也兼顾了当前负载,提高了集群系统的整体性能。     

基于内存云的大块数据对象并行存取策略

由于内存云(RAMCloud)只支持最大1 MB的小块数据对象存储,因此当大于1 MB的对象需要存储在内存云集群中就会受到对象大小的限制,无法在集群中进行存储。为了解决内存云存储限制的问题,提出了基于内存云的大块数据对象并行存取策略。该存储策略首先将大块数据对象分割成若干个1 MB的小块数据对象,然后在客户端生成数据摘要,最后使用并行存储算法将客户端分割成的小块数据对象存储在内存云集群中。读取时首先读取数据摘要,然后根据数据摘要从内存云集群中并行读取小块数据对象,并将小块数据对象合并生成大块数据对象。实验结果表明:大块数据对象的并行存取策略在不破坏内存云集群体系结构的前提下存储时间为16~18 μs,读取时间为6~7 μs。在InfiniBand网络架构下,所提并行算法的加速比呈现类似线性的增长,它使大块数据对象也能够像小块数据对象一样在微秒级别下快速、高效地进行存取。     

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.