Linux下高效可靠的应用同步升级技术

为了能够向用户提供既可靠又高效的系统及软件更新方法,我们设计了以镜像源管理服务器为主的软件更新方案。本文详细介绍了镜像源管理服务器技术的设计方案,并对技术方案进行了理论分析,对技术方案的验证方法和验证结论做了详细的分析和说明。镜像源管理服务器技术在实现中,相较于当前Linux通用的镜像源更新方案,能够避免单一镜像源更新不够及时的问题、源服务器网络负载过高问题,为用户提供稳定且快速的资源下载。     

三方面顾安全

北京市公安局出入境管理处的办公自动化网络建于1998年,在局域网络中的服务器主要包括:数据库服务器,内部 Web 服务器,外部 Web 服务器及 E-mail 服务器、财务软件服务器等,其中数据库服务器为 Compaq公司生产的 Alpha Server4100,安装 Compaq Unix 操作系统,Oracle 数据库,完成全部涉外系统数据的存储。信息中心在系统建设初期曾采取了许多防范措施,例如,利用数据库服务器 Alpha Server 4000的软件镜像技术,实现硬盘的镜像,保护数据。但是,这种技术存在着很多的局限性,包括:服务器可扩充磁盘数量有限,镜像技术使系统消耗一半数量的磁盘用于备份。镜像技术不能将操作系统备份,这样一旦系统故障,将导致业务终断,必须耗费一定的时延恢复系统。镜像技术     

光盘镜像服务器的Cache技术研究与实现

本文提出了一种基于光盘镜像服务器系统的两级Cache结构，即在客户端建立一个小的Cache，通过预取机制增大一次请求的规模；同时，在服务器端设计一个大的Cache，加快数据请求的响应速度。实验证明，两级Cache结构大大提高了光盘镜像服务器系统的数据传输率。     

高性能光盘镜像服务器的研究与实现

随着网络上光盘资源的增长，光盘镜像服务器成为光盘网络接享的重要技术。针对传统光盘镜像服务器的缺点，文章实现了一个新的基于iSCSI协议思想的高性能光盘镜像服务器，详细介绍了这种光盘镜像服务器的设计方案，并进行了相应的试验测试和性能分析。     

Novell网络服务器中双硬盘维护数据

随着计算机应用的普及，很多单位及部门都纷纷建立K级的局域网络系统，如企业单位的管理系统、工程设计系统、图书管理系统等等。我们在享用计算机管理的快速高效、智能等强大功能时，不得不担心文件服务器的可靠性。倘若服务器的数据一旦丢失，带来的是难以估量的严重后果。现在硬盘价格日趋下降，推荐文件服务器采用在必要时能独立引导启动运行的双硬盘镜像系统，并在硬盘开辟数据备份卷，可快速简易地定期备份重要的数据，甚至备份系统卷。万一文件服务器主硬盘损坏不能使用时，不至于数据尽失。当改镜像硬盘为主硬盘，重新启动系统后，…     

自定义镜像为下载提速

FlashGet的镜像功能可以从不同的服务器上下载同一个文件,并可根据服务器的响应速度自动选择较快的服务器。但是镜像功能默认使用的镜像服务器地址都是由安装目录的"mirrors.lst"文件控制,其中的镜像服务器地址都是固定的,限制了使用。在1.8版本中,FlashGet允许自行添加新的镜像服务器地址,只要按一定的格式编辑安装目录中的"mymirror.lst"文件即可。     

NOVELL网文件服务器的快速复制方法

MethodofRapidlyDuplicatingNovellFileServerLiLupunNOVELL网络以其安全性好、硬件投资少、易于管理维护等特点，在全世界拥有极高的占有率。目前，我国多数院校将其作为公用机房管理的首选系统。我们知道，安装NOVELL文件服务器、安装应用软件、建立用户帐号等工作至少要花费系统管理员数小时的工作。由此看来，有必要找到一种快速安装文件服务器的方法。一些国内计算机杂志曾介绍使用文件服务器卷镜像的方法来复制文件服务器。这种方法虽简单可行，但仍存在一定的局限性：其一：镜像磁盘与被镜像磁盘的卷大小必须相等；其二：镜…     

虚拟镜像光盘网络服务器的设计与实现

提出并实现了一种具有较高性能价格比的、基于PC的虚拟镜像光盘网络服务器方案。该虚拟光盘网络服务器具有如下优点：支持多种格式盘片的镜像读取；支持多种网络协议；虚拟光盘镜像服务器在功能上完全独立于网络上的主服务器；价格低廉，无须特殊硬件等。初步实验验证了该方案的可行性。由于该方案具有很好的应用前景，正准备将其推向市场。     

丸子在线

问:现在很多网站都说自己有镜像站点.请问何为镜像? 　　答:镜像在网络中主要是对于网站来说的,与主网站的内容相同的其它位置的网站就叫做镜像网站.比如,我有一个主网站放在A服务器,同时我也把此网站内容复制到另一个B服务器,但两者的网址与域名不同,那么B服务器里的网站就叫做A服务器的主网站的镜像.……     

光盘共享设备如何选之应用篇

清华同方徐学雷博士: 用户选择光盘镜像服务器时主要应从容量、速度和价格三方面考虑。光盘镜像服务器的容量主要取决于内置的硬盘数量和大小。有些厂家的光盘镜像服务器在厂岀时已经预置了一定容量的硬盘,如果用户需要扩容,可将光盘镜像服务器上的可插拔硬盘盒抽岀,自行安裝硬盘进行扩容。     

Performance analysis of advanced I/O architectures for PC-based video servers

In the personal computing and workstation environments, more and more I/O adapters are becoming complete functional subsystems that are intelligent enough to handle I/O operations on their own without much intervention from the host processor. The IBM subsystem control block (SCB) architecture has been defined to enhance the potential of these intelligent adapters by defining services and conventions that deliver command information and data to and from the adapters. In recent years, a new storage architecture, the redundant array of independent disks (RAID), has been quickly gaining acceptance in the world of computing. In this paper, we discuss and present a performance analysis of the SCB architecture and disk array technology in typical video server environments. In particular, we would like to see whether a disk array can outperform a group of disks (of the same type, the same data capacity, and same cost) operating independently (not in parallel as in a disk array) in a video server environment where most disk I/O operations are large sequential reads.     

IOMan:一种支持多操作系统远程启动和运行的I/O管理方法

为了降低用户使用和维护计算机系统的成本,基于透明计算模式提出了一种工作在局域网环境下的I/O管理方法:IOMan. IOMan只是用软件方法在客户端设置磁盘I/O重定向机制,按需动态下载数据,而不需要修改当前常用的操作系统如Windows的启动机制,也不影响其他I/O操作,能够支持多种操作系统的远程启动和应用程序的运行 . IOMan基于客户机/服务器模型,包括I/O Client和I/O Server两个部分,其中I/O Client工作在客户端,I/O Server工作在服务器端 . I/O Client通过重新定义访问磁盘的BIOS中断处理程序以及创建虚拟本地磁盘,将I/O请求发送给服务器;I/O Server响应客户端请求,读写服务器上存储的虚拟硬盘文件,然后以扇区形式将数据发送给I/O Client.     

一种基于节的视频服务器允许接纳控制算法

提出了一种基于“服务器节”的支持压缩多媒体流的服务器中CPU、磁盘、网络和内存等资源管理的方法和允许接纳控制算法。“服务器节”概念定义了一组客户视频服务特性,如播放、快进、慢进和暂停等,并且确定了视频服务所需资源的分配参。一个“服务器节”包括视频服务器、磁盘设备、网络设备和允许接纳控制。它不但能优化使用单个资源,对于给定系统支持最大数量的客户端,保证其服务质量（QoS),而且其允许接纳控制算法能根据系统所有资源的状况,在不影响原有的视频服务基础上,确定对客户端新提出的视频服务是否接受。     

Constructing a video server with tertiary storage: Practice and experience

Handling a tertiary storage device, such as an optical disk library, in the framework of a disk-based stream service model, requires a sophisticated streaming model for the server, and it should consider the device-specific performance characteristics of tertiary storage. This paper discusses the design and implementation of a video server which uses tertiary storage as a source of media archiving. We have carefully designed the streaming mechanism for a server whose key functionalities include stream scheduling, disk caching and admission control. The stream scheduling model incorporates the tertiary media staging into a disk-based scheduling process, and also enhances the utilization of tertiary device bandwidth. The disk caching mechanism manages the limited capacity of the hard disk efficiently to guarantee the availability of media segments on the hard disk. The admission controller provides an adequate mechanism which decides upon the admission of a new request based on the current resource availability of the server. The proposed system has been implemented on a general-purpose operating system and it is fully operational. The design principles of the server are validated with real experiments, and the performance characteristics are analyzed. The results guide us on how servers with tertiary storage should be deployed effectively in a real environment. RID="*" ID="*" e-mail: hjcha@cs.yonsei.ac.kr     

A Design Framework for Multi-Resolution Video Servers

Video can be encoded into multiple-resolution format in nature. A multi-resolution or scalable video stream is a video sequence encoded such that subsets of the full resolution video bit stream can be decoded to recreate lower resolution video streams. Employing scalable video enables a video server to provide multiple resolution services for a variety of clients with different decoding capabilities and network bandwidths connected to the server. The inherent advantages of the multi-resolution video server include: heterogeneous client support, storage efficiency, adaptable service, and interactive operations support.For designing a video server, several issues should be dealt with under a unified framework including data placement/retrieval, buffer management, and admission control schemes for deterministic service guarantee. In this paper, we present a general framework for designing a large-scale multi-resolution video server. First, we propose a general multi-resolution video stream model which can be implemented by various scalable compression techniques. Second, given the proposed stream model, we devise a hybrid data placement scheme to store scalable video data across disks in the server. The scheme exploits both concurrency and parallelism offered by striping data across the disks and achieves the disk load balancing during any resolution video service. Next, the retrieval of multi-resolution video is described. The deterministic access property of the placement scheme permits the retrieval scheduling to be performed on each disk independently and to support interactive operations (e.g. pause, resume, slow playback, fastforward and rewind) simply by reconstructing the input parameters to the scheduler. We also present an efficient admission control algorithm which precisely estimates the actual disk workload for the given resolution services and hence permits the buffer requirement to be much smaller. The proposed schemes are verified through detailed simulation and implementation.     

Performance analysis of mass storage service alternatives fordistributed systems

The authors consider the performance of alternative mass-storage services for a client-server-style distributed system. Some qualitative arguments are presented on the ramifications of implementations of mass-storage services at various levels of the storage semantics hierarchy. The authors concentrate, in particular, on contrasting disk and file services. The functionalities of disk and file services are distinguished by their primitive operations: individual disk-block access for the disk service, and individual file-block access for the file service. This difference results in different partitionings of the computation between the client and server, as well as different network communication requirements. To understand the ramifications of such differences between the services, the authors present performance estimates for basic disk and file services. Performance estimates for several design alternatives are presented     

一种基于VirtFS的共享文件空间技术

由于虚拟环境多次I/O操作模拟的存在,运行在宿主服务器中的各虚拟客户机之间使用传统代理进行文件访问效率不高。为此,提出了基于VirtFS的共享文件空间技术。构建了虚拟客户机共享文件空间的系统架构,设计了虚拟磁盘操作映射机制,使用VirtFS框架提供的系统层接口,在宿主服务器中的VirtFS服务端截取和映射文件操作,直接将虚拟机文件系统的操作映射为对宿主服务器文件系统的操作。为了保障安全,彻底隔离用户域,实现分组共享。实验结果表明,采用该方法比现有代理方法文件读写效率分别提高9.7和5.7倍。     

Dynamic cluster resource allocations for jobs with known andunknown memory demands

The cluster system we consider for load sharing is a compute farm which is a pool of networked server nodes providing high-performance computing for CPU-intensive, memory-intensive, and I/O active jobs in a batch mode. Existing resource management systems mainly target at balancing the usage of CPU loads among server nodes. With the rapid advancement of CPU chips, memory and disk access speed improvements significantly lag behind advancement of CPU speed, increasing the penalty for data movement, such as page faults and I/O operations, relative to normal CPU operations. Aiming at reducing the memory resource contention caused by page faults and I/O activities, we have developed and examined load sharing policies by considering effective usage of global memory in addition to CPU load balancing in clusters. We study two types of application workloads: 1) Memory demands are known in advance or are predictable and 2) memory demands are unknown and dynamically changed during execution. Besides using workload traces with known memory demands, we have also made kernel instrumentation to collect different types of workload execution traces to capture dynamic memory access patterns. Conducting different groups of trace-driven simulations, we show that our proposed policies can effectively improve overall job execution performance by well utilizing both CPU and memory resources with known and unknown memory demands     

磁道复制--多媒体数据读取的磁盘寻道优化策略

由于寻道是磁盘I／O操作中的主要浪费之一,采用磁道复制可以减少寻道．针对单盘与盘阵情况,磁道复制可以有两种不同的方法：n-way和n-d-way,并经推导可得出二者平均寻道距离的解析表达式.进行的模拟实验不仅证明了解析表达式的准确性,而且表明在相同的空间开销下,磁道复制策略比传统的以空间换取时间的策略如n-way striping和D-way mirror有更少的寻道距离．     

Efficient support for interactive operations in multi-resolution video servers

In this paper, we present a placement algorithm that interleaves multi-resolution video streams on a disk array and enables a video server to efficiently support playback of these streams at different resolution levels. We then combine this placement algorithm with a scalable compression technique to efficiently support interactive scan operations (i.e., fast-forward and rewind). We present an analytical model for evaluating the impact of the scan operations on the performance of disk-arr ay-based servers. Our experiments demonstrate that: (1) employing our placement algorithm substantially reduces seek and rotational latency overhead during playback, and (2) exploiting the characteristics of video streams and human perceptual tolerances enables a server to support interactive scan operations without any additional overhead.