集群服务器文件动态分配的改进算法

在分析MMPacking算法的基础上，提出了一种改进的文件分配算法。在按照MMPacking算法分配文件时，根据节点的文件累积需求度去完成文件的分配或复制，考虑了节点的剩余能力。文件分配在所有服务器节点中周期性地进行，每进行了一轮文件分配后，都要从第1个节点开始新的一轮分配。在开始新一轮分配前，服务器节点要按照服务器的剩余能力重新进行降序排列。在每轮分配中，每分配一次文件到某个服务器节点后，都要检测当前节点服务器的剩余能力是否大于下一节点的剩余能力，如果满足条件，则将重新开始新的一轮文件分配。改进后的算法降低了由于客户需求或服务器配置变化所要支出的额外成本，有效地达到了负载均衡的目的。仿真结果表明，改进后的算法优于MMPacking 算法。     

如何修复“文件分配表损坏”

早晨起来，开机电脑显示“File Allocation Table bad driver C:”，我想应该是“文件分配表损坏”，但除了重装Windows之外不知道有没有什么比较简单的办法？（上海 天 寅） 该问题确实是系统C盘的文件分配表损坏了。文件分配表（FAT）是MS-DOS和其他基于Windows的操作系统用来组织和管理文件的文件系统。当你通过使用FAT或FAT32文件系统格式卷时，文件分配表是Windows创建的数据结构。Windows在FAT中存储关于每个文件的信息，以供检索文件之用。FAT32比FAT支持更小的簇和更大的卷，这就使得FAT32卷的空间分配更有效率。 你…     

集群计算并行I/O中动态文件分配策略

针对集群计算系统中并行I／O文件分配问题进行了研究，提出一种新的动态文件分配算法一启发式负载与服务时间变化综合平衡策略。该策略将所需要的访问服务时间相似的文件分配到集群系统的同一结点磁盘上，并保证每个磁盘上的负载值不超过负载平衡的极限值，从而在所有结点磁盘间既基本实现负载均衡，又使每个磁盘上文件间的服务时间变化最小化。实验结果表明了该策略在性能提高方面的有效性。     

大量数据处理时的高效率VC++编程方法

Visual C＋＋是目前计算机软件设计中最流行的、功能强大的常用开发工具。本文针对VC＋＋在开发大数据量处理的软件时，存在内存分配、绘图性能、文件存取等方面的问题，分别提出虚拟内存分配、双缓冲绘图、巨型文件读写等解决办法。     

控制磁盘文件的存放位置

控制磁盘文件的存放位置云南省电力设计院潘伟康在ＭＳ—ＤＯＳ中，创建一个文件时，ｔｏｓ就为此文件分配盘空间，分配的最小单位是簇，用户并不能参与这种分配，通常也无需关心这种分配。但有时为了特殊目的，要把文件存放在某固定的区域内，例如，临时需要把某软件装人...     

恢复被损坏磁盘上的中西文文本文件

磁盘的引导扇区、文件分配表或根目录区被破坏，常会引起存储于磁盘上的文件不能用DOS命令读写，或读写结果不正确，甚至文件名从磁盘目录区中消失等问题。此时，要有效地恢复文件是困难的。有的用户采用确定文件位置后重填目录项和文件分配表的方法来恢复文件。笔者则利用文本文件的内容可以在屏幕上显示的特点，编制了一个TurboC实用程序，来恢复文本文件。这种方法简便可行，现介绍于下。我们知道，磁盘上的内容是由引导扇区、文件分配表、根目录区和数据区这4部分组成的。其中前三者常由于病毒感染等原因被破坏，但数据区的内容往往完…     

磁盘文件占用空间计算方法

一个文件在磁盘上占用的空间与该文件的实际长度是两个不同的概念。文件的实际长度固定不变，但在磁盘上占用的空间大小则与所用机型、DOS版本号及介质环境的不同而不同，了解文件在磁盘中占用空间的分配，对于管理开发应用软件，有效地利用资源具有重要意义。我们知道，DOs在磁盘上存储文件的过程有三步：一是把文件名、文件长度及文件性质等物理特征登录在DOs的目录区；二是把文件内容占用磁盘位置登录在文件分配表＊AT上；三是把文件内容写入相应的磁盘扇区中。因此，文件分配表＊＊T决定着文件在磁盘上的实际空间。可见，文件占用的…     

一种集群计算系统中并行I/O文件存储分配策略

现代计算机系统性能已经由受限于CPU转变为受限于I／O，近年来研究人员对高性能计算中的并行I／O问题进行了深入研究．本论文的主要工作是对集群计算中的并行I／O子系统进行研究，提出一种文件拆分与存储分配的新策略，即：已知知识的文件拆分与分配方法(KKFDA)，该方法保证文件存储方式与访问方式的一致性，达到了提高文件访问时的本地命中率、缩短访盘响应时间的目的．算法设计与实验证明了方法的有效性．     

文件分配问题的一种动态解决算法

文件分配问题 (FAP)是计算机网络和分布式系统优化中的经典问题 .分析了 FAP的主要特征 ,提出了一种需求驱动的动态分配算法 ,该算法避免了复杂的运算 ,参数较少且容易采集 ,既能进行文件分配 ,也能回收闲置文件副本 .仿真实验表明 ,该算法在负载平衡、吞吐率和响应时间等方面有明显优势     

通用文件备份程序的设计

本文介绍了一个通用文件备份程序，利用该程序可实现：自动分配文件，多张软盘复制的功能     

A model for database allocation incorporating a concurrency controlmechanism

The impact of incorporating a specific concurrency control mechanism (CCM) into the file allocation problem (FAP) is discussed. Depending on the specific CCM use, the communication flows in a network will vary. To allocate data optimally, one must identify the exact communication flows in the network. It is this aspect that has been ignored in past research on the FAP. A linear mixed-integer programming model formulated for the FAP is given. The model incorporates the WRITE LOCKS ALL-READ LOCKS ONE mechanism for concurrency control. A special algorithm based on the implicit representation of variable upper bounds is developed to solve the model. Detailed analysis for various configurations of a network is performed. Several potential applications for the model are identified     

Exact approaches for static data segment allocation problem in an information network

In a large distributed database, data are geographically distributed across several separate servers (or data centers). This helps in distributing load in the access network. It also helps to serve data locally where it is required. There are various approaches based on the granularity of data for efficient data distribution in a communication network. The file allocation problem (FAP) locates files to servers, the segment allocation problem (SAP) locates database segments, and the mirror location problem (MLP) locates replicas of the entire database. The placement of such data to multiple servers can be modeled as an optimization problem. The major decisions influencing optimization involves the location of servers, allocation of content and assignment of users. In this paper, we study the segment allocation problem (SAP), which is also known as the partial mirroring problem. This approach is more tractable than the file allocation problem in realistic cases and also eliminates the overhead of (constant) update costs that is incurred in the mirror location problem. Our contribution is two-fold: Firstly, earlier works on SAP assume pre-defined segments. We build a data partitioning method using well-known facility location models. We quantify the performance of the partitioning method. We show that the method partitions the database within a reasonable limit of error. Secondly, we introduce a new model for the segment allocation problem in which the segments are completely connected to each other by high-bandwidth links and contains a cost benefit for inter-segment traffic flows. We formulate this problem as an MILP and build exact solution approaches to solve large scale problems. We demonstrate some structural properties of the problem that make it solvable, using a Benders decomposition algorithm. Computational results validate the superiority of the decomposition approach.     

Optimal bucket allocation design of k-ary MKH files for partialmatch retrieval

The paper first shows that the bucket allocation problem of an MKH (multiple key hashing) file for partial match retrieval can be reduced to that of a smaller sized subfile, called the remainder of the file. And it is pointed out that the remainder type MKH file is the hardest MKH file for which to design an optimal allocation scheme. The authors then particularly concentrate on the allocation of an important remainder type MKH file; namely, the k-ary MKH file. They present various sufficient conditions on the number of available disks and the number of attributes for a k-ary MKH file to have a perfectly optimal allocation among the disks for partial match queries. Based upon these perfectly optimal allocations, they further present a heuristic method, called the CH (cyclic hashing) method, to produce near optimal allocations for the general k-ary MKH files. Finally, a comparison, by experiment, between the performances of the proposed method and an “ideal” perfectly optimal method, shows that the CH method is indeed satisfactorily good for the general k-ary MKH files     

多层级设施选址-路径规划问题建模及算法

基于有向图对物流网络多层级设施选址-路径规划问题,建立混合整数规划数学模型,提出量子进化算法与遗传算法协同的双智能算法集成求解方案.量子进化算法解决设施选址和设施分配,遗传算法进行路径规划,并提出可达配送区域的搜索策略和路径长度为权重的设施分配优化策略以提高算法效率.实例测试表明,所提出的数学模型和组合智能算法是可行而有效的,可为多层级设施选址-路径规划问题提供理论与方法指导.     

Dynamic storage allocation: Experiments using the c language

The paper discusses the problem of dynamic storage allocation (DSA) using C in a VMS environment. The problem is studied in a specific context, i.e. fault simulation of logic circuits. However, owing to its intrinsic generality, the adopted solution can be effectively applied to a large number of similar situations. It is shown how the use of standard C-functions for dynamic memory allocation result unacceptable for efficiency reasons and different implementation strategies to solve the problem are presented.     

Evaluation of the File Redundancy in Distributed Database Systems

This paper treats the file redundancy issue in distributed database systems, asking what is the optimal number of file copies, given the ratio r of the frequency of update requests to the frequency of all file access requests (i.e., queries and updates). Formulations of this type of problem, including optimal file allocation, have been attempted by a number of authors, and some algorithms have been proposed. Although such algorithms can be used to solve particular problems, it seems difficult to draw general conclusions applicable to a wide variety of practical distributed database systems. To probe into this hard to formulate but interesting problem, our paper constructs simplified network models of distributed database systems, and computes the optimal number of file copies, as well as their locations, to minimize the communication cost. For several network types, we plot the optimal number of file copies as a function of the ratio r.     

On the design of multiple key hashing files for concurrent orthogonal range retrieval between two disks

This paper concerns the following problem: given a set of multi-attribute records, a fixed number of buckets and a two-disk system, arrange the records into the buckets and then store the buckets between the disks in such a way that, over all possible orthogonal range queries (ORQs), the disk access concurrency is maximized. We shall adopt the multiple key hashing (MKH) method for arranging records into buckets and use the disk modulo (DM) allocation method for storing buckets onto disks. Since the DM allocation method has been shown to be superior to any other allocation methods for allocating an MKH file onto a two-disk system for answering ORQs, the real issue is knowing how to determine an optimal way for organizing the records into buckets based upon the MKH concept.

A performance formula that can be used to evaluate the average response time, over all possible ORQs, of an MKH file in a two-disk system using the DM allocation method is first presented. Based upon this formula, it is shown that our design problem is related to a notoriously difficult problem, namely the Prime Number Problem. Then a performance lower bound and an efficient algorithm for designing optimal MKH files in certain cases are presented. It is pointed out that in some cases the optimal MKH file for ORQs in a two-disk system using the DM allocation method is identical to the optimal MKH file for ORQs in a single-disk system and the optimal average response time in a two-disk system is slightly greater than one half of that in a single-disk system.     

Scalable, statistical storage allocation for extensible inverted file construction

An Inverted file is a commonly used index for both archival databases and free text where no updates are expected. Applications like information filtering and dynamic environments like the Internet require inverted files to be updated efficiently. Recently, extensible inverted files are proposed which can be used for fast online indexing. The effective storage allocation scheme for such inverted files uses the arrival rate to preallocate storage. In this article, this storage allocation scheme is improved by using information about both the arrival rates and their variability to predict the storage needed, as well as scaling the storage allocation by a logarithmic factor. The resultant, final storage utilization rate can be as high as 97-98% after indexing about 1.6 million documents. This compares favorably with the storage utilization rate of the original arrival rate storage allocation scheme. Our evaluation shows that the retrieval time for extensible inverted file on solid state disk is on average similar to the retrieval time for in-memory extensible inverted file. When file seek time is not an issue, our scalable storage allocation enables extensible inverted files to be used as the main index on disk. Our statistical storage allocation may be applicable to novel situations where the arrival of items follows a binomial, Poisson or normal distribution.     

用遗传算法解决基于分条技术的磁盘负载均衡问题

如何提高存储子系统的I／O性能一直以来都是计算机领域的一个研究热点，而目前提高存储子系统的I／O性能的一个最大障碍就是负载不均衡．文章通过研究磁盘负载均衡问题，提出了一种采用遗传算法来实现基于分条技术的磁盘动态负载均衡算法．该方法包括基于分条技术的文件划分算法和为实现负载均衡的文件分配算法．根据遗传算法对种群进行编码、选择、杂交操作和变异操作，从而产生出满足负载均衡条件的映射方案．最后通过实验仿真证明该算法止确有效．     

网络传输层访问请求控制的实现方法

防范计算机敏感信息泄漏已成为当前信息安全保障工作中急需解决的问题,但现有的信息安全产品大多数是防范黑客和病毒攻击的,不能有效防止敏感数据泄漏。针对上述情况,本文提出了一种计算机数据安全管理系统,系统从USB移动存储介质安全认证与使用控制、基于传输层访问请求的磁盘文件保护以及网络安全监控等方面入手,对传输层访问请求的网络行为进行安全监管,堵住容易引起敏感信息泄漏的安全漏洞,有效保证了计算机数据的安全。