Product Profile

Floppy Disk Drive: FD360 micro-peripheral floppy disk drive operates under directions from Intel or National Semiconductor microprocessor system. Hardware interfaces and FDOS (Floppy Disk Operating Systems) available for Intellec-8, Intellec-8/Mod-80, IMP-16P, 16L, 8P. Features include format compatibility with IBM 3741, 3742, 3540 systems, built-in hardware track seek and seek verification, automatic head load/unload, operation with programmed I/O or DMA interfaces, sector buffering to enable asynchronous programmed I/O. Eight input, 16 output lines provide interfacing. Single drive configuration, $2350 (unit); 2 drives, $3000. Special interfaces available. – iCOM, Canoga Park, CA.     

New Products

The Model 121 "Naked" Floppy Disk Controller is a multipurpose, multi-drive floppy disk memory device aimed at both microprocessor and minicomputer applications. According to the manufacturer, the unit is compatible with DMA channels as well as programmed I/O channels, interfaces with most minicomputers and microprocessors, and can be made software-compatible with existing disk systems.     

基于OpenSSD的闪存转换算法优化

随着信息技术的快速发展,数据存储的需求日益增长,人们对硬盘读写性能的要求越来越高.相比于机械硬盘,固态硬盘可靠性高、能耗低,无寻道时间开销,逐渐取代机械硬盘成为主流的存储介质.但固态硬盘访问数据时需要经过转换,对应的闪存转换算法对读写性能影响很大.OpenSSD项目提供了一个可开发SSD固件的平台,基于此平台本文针对其上的闪存转换算法进行研究并优化,分析了影响I/O读写性能的各类因素,设计出一种适合Cosmos OpenSSD的缓存管理和闪存管理方法,大幅提高了Cosmos OpenSSD的性能.     

Windows Vista存储管理新技术研究

微软在Vista中采用了较多的存储管理新技术。使用SuperFetch、ReadyBoost、ReadyDrive三大存储管理新技术加速系统,提升系统性能。设计磁盘I/O优先级策略,区别对待磁盘I/O请求,提高系统响应能力,克服磁盘I/O瓶颈。利用BitLocker磁盘驱动器加密技术,配合改良的加密文件系统EFS,满足磁盘数据存储的安全性需求。Vista采用了许多类似的新技术,而且大多数技术在Windows7中得到了继承和发展,研究Vista具有十分重要的意义。     

WindowsNT环境下缓存磁盘技术驱动程序的设计与实现

随着计算机性能的迅速提高,系统越来越强烈地要求所配置的高速外存储器有更好的联机性能,I／O性能增长与CPU速度增长的严重失配,使I／O并颈问题日超严重,本文研究了Windows NT系统下的一种用来改善磁盘小写I／O（写请求的长度小于16K）性能的新途径0－缓存磁盘技术,它采用了多级Cache的存储思想,在办公／工程负载环境中的
峰值性能相对于常规磁盘有很大的提高。本文深入了研究了缓存磁盘技术在Windows NT环境下驱动程序的结构和原理,并详细阐述了具体的实现机制和方法。     

Exploiting the performance gains of modern disk drives by enhancing data locality

Due to the widening performance gap between RAM and disk drives, a large number of I/O optimization methods have been proposed and designed to alleviate the impact of this gap. One of the most effective approaches of improving disk access performance is enhancing data locality. This is because the method could increase the hit ratio of disk cache and reduce the seek time and rotational latency. Disk drives have experienced dramatic development since the first disk drive was announced in 1956. This paper investigates some important characteristics of modern disk drives. Based on the characteristics and the observation that data access on disk drives is highly skewed, the frequently accessed data blocks and the correlated data blocks are clustered into objects and moved to the outer zones of a modern disk drive. The idea attempts to enhance spatial locality, improve the efficiency of aggressive sequential prefetch, and take advantage of Zoned Bit Recording (ZBR). An experimental simulation is employed to investigate the performance gains generated by the enhanced data locality. The performance gains are analyzed by breaking down the disk access time into seek time, rotational latency, data transfer time, and hit ratio of the disk cache. Experimental results provide useful insights into the performance behaviours of a modern disk drive with enhanced data locality.     

Product Profile

High Speed Paper Tape Reader: Model R8016P-designed for direct interface with National Models IMP-8P and IMP-16P. Features include: assembler program loading in less than 120 secs; use of photo-electrical character detector for more reliable loading; a 40-line ribbon cable that directly interfaces with National unit; and complete software package that works with National software. Includes manual tape-advance push-button on front panel to allow easy removal of tapes. Reader is assembled in a stand-alone cabinet that measures 17 X 8 X 5 1/4"; available in an optional 19" RETMA rack mount. Power requirements: 115V, 60 Hz, single phase with optional 220V, 50 Hz models available. Price: $895. – iCOM, Inc., Canoga Park, CA.     

基于存储熵的存储负载均衡算法

在分布式存储系统中,一般都是以磁盘空间利用率（DU）来判断各存储节点的负载均衡程度,当所有节点的磁盘空间利用率相等时,是整个分布式存储系统的存储负载均衡点。但是在实际的应用场景中,磁盘I/O速率比较低的存储节点和可靠性比较低的存储节点往往成为影响整个存储系统数据读写性能的瓶颈,因此在异构分布式存储系统中,特别是各存储节点磁盘I/O速率和可靠性差异较大的分布式存储系统中,如果仅仅以磁盘空间利用率作为存储负载均衡的判定条件,则其数据的读写效率必然受到限制。从读写效率的角度提出一种度量分布式存储系统中存储负载均衡的新思路。根据负载均衡理论和熵理论给出存储熵（SE）的定义,并提出一种基于存储熵的负载均衡算法,该算法通过系统负载判定、单节点负载判定和负载迁移实现了对分布式存储系统存储负载的量化调整,并通过实验与基于磁盘空间利用率的负载均衡算法进行了对比分析,验证了该算法对分布式存储系统中存储负载具有良好的均衡性,有效地控制了系统负载失衡的问题,提高了分布式存储系统的整体读写效率。     

A new direct Seek Control Design of Optical Disk Drives

This paper is concerned with the seek control of Optical Disk Drives (ODDs). We propose a direct Seek Control Scheme (SCS) that provides fast data access capability and robust stability for high-performance Optical Disk Drives. Although an optical disk drive has a significant advantage of random accessibility, increased rotational speed of a disk and limitations of mechanical structure always make it impossible for the conventional SCS to achieve stable and satisfactory seek performance. The conventional seek control technique utilizes only the coarse actuator without any maneuvering of the fine actuator. In this paper, we analyze the problems that may arise when the conventional SCS is applied to high-speed rotational ODD and propose a new SCS that employs both the coarse and fine actuators. With assistance of the fine actuator, however, the seek control system is designed such that its performance is guaranteed for various disturbances and mechanical limitations. Simulations and experiments show the improvements of the proposed direct SCS implemented on a practical DVD-ROM drive system.     

Product Profile

High Speed Paper Tape Reader: Model R8016P—designed for direct interface with National Models IMP-8P and IMP-16P. Features include: assembler program loading in less than 120 secs; use of photo-electrical character detector for more reliable loading; a 40-line ribbon cable that directly interfaces with National unit; and complete software package that works with National software. Includes manual tape-advance push-button on front panel to allow easy removal of tapes. Reader is assembled in a stand-alone cabinet that measures 17 X 8 X 5 ¼"; available in an optional 19" RETMA rack mount. Power requirements: 115V, 60 Hz, single phase with optional 220V, 50 Hz models available. Price: $895. – iCOM, Inc., Canoga Park, CA.     

存储设备块重组机制仿真研究

为了提高存储设备的I/O性能,设计了一种新的基于语义的块重组机制.该机制作为语义智能磁盘技术的一种应用,可以利用文件系统的语义信息推断磁盘块的相关性,并将语义相关的块移动到临近区域.块重组机制减少了访问文件时所需的寻道次数,提高了I/O性能.与其他块重组方法相比,该机制不依赖于历史访问信息,并且不受负载变化影响.通过仿真实验对该机制进行评测,实验结果表明,块重组机制能够有效减少I/O次数.     

基于连接管理的并行I／O数据库系统的研究

I／O和网络开销是数据库系统主要的性能瓶颈，本文针对数据库I／O请求的特点，讨论在大量并发I／O请求到来的情况下如何有效地对这些I／O请求进行重组、排序和合并，以便提高数据库系统的总体性能。     

16＊16点阵显示汉字的分析与制作

本文利用AT89c51作为控制芯片,将广泛使用的88的点阵组合成16＊16的汉字显示屏和串并转换驱动芯片74HC595芯片来完成显示复杂图形,并能在通过按键加快、减慢汉字移动速度的目标,设计极大节省了控制芯片的I／O资源。     

Do It Yourself Haptics: Part II

This article is the second of a two-part series intended to be an introduction to haptic interfaces, their construction, and application design. Haptic interactions employ mechanical, programmed physical devices that can be used for human-computer communication via the sense of touch. In Part I of this series, we focused on the devices themselves: the classes of hardware schemes currently available or envisioned, the software components that drive them, and specific examples that can be built on the kitchen table. Here in Part II, we broach a topic that is coming into its own; between the vision of a particular utility that haptic feedback theoretically should enable and the hardware capable of delivering the required sensations is the problem of designing the interaction in a usable way.     

A disk bandwidth allocation mechanism with priority

Virtualization is a popular technology. Services and applications running on each virtual machine have to compete with each other for limited physical computer or network resources. Each virtual machine has different I/O requirement and special priority. Without proper scheduling resource management, a load surge in a virtual machine may inevitably degrade other’s performance. In addition, each virtual machine may run different kinds of application, which have different disk bandwidth demands and service priorities. When assigning I/O resources, we should deal with each case on demand. In this paper, we propose a dynamic virtual machine disk bandwidth control mechanism in virtualization environment. A Disk Credit Algorithm is introduced to support a fine-gained disk bandwidth allocation mechanism among virtual machines. We can assign disk bandwidth according to each virtual machine’s service priority/weight and its requirement. Related experiments show that the mechanism can improve the VMs’ isolation and guarantee the performance of the specific virtual machine well.     

Fast-path I/O architecture for high performance streaming server

In a disk-network scenario where expensive data transfers are the norm, such as in multimedia streaming applications, for example, a fast-path I/O architecture is generally considered to be “good practice.” Here, I/O performance can be improved through minimizing the number of in-memory data movements and context switches. In this paper, we report the results of the design and implementation of a high-performance streaming server using cheap hardware units assembled directly on a test card (i.e., NS card). The hardware part of our architecture is open to further reuse, extension, and integration with other applications even in the case of inexpensive and/or faster hardware. From the viewpoint of software-aided I/O, we offer Stream Disk Array (SDA) for scatter/gather-style block I/O, EXT3NS multimedia file system for large-scale file I/O, and interoperable streaming server for stream I/O.     

Interfacing transputer links to external devices

Two approaches to interfacing transputers to external circuitry are considered. The design and construction of both a serial and a parallel interface for transputers is described. These enable transputers to communicate with peripherals via the standard Inmos transputer links. A Motorola MC68701 8-bit microcomputer, serving as a programmable I/O controller, is incorporated into both interfaces. This solution lends a high degree of flexibility into the interface design, and can be used with any transputer board which has spare links available at edge connectors. Finally, two control applications are briefly described which utilize the interfaces.     

异构盘阵中最优Stripe Unit Size选择技术

缓解计算机IO子系统瓶颈的有效手段是采用磁盘阵列，配置时，SUS(Stripe Unit Size)的选择对盘阵性能的影响非常关键，而以往对异构盘阵的SUS的选择研究较少，该文推导出了确定异构盘阵最优SUS的方程，具体工作如下：首先，该文采用close队列网络模型来描述异构盘阵负载；然后，从该模型推导出系统数据传输率解析表达式，根据该表达式和异构盘阵中设备的特性，可求出使传输率最大的SUS，最后，研究中进行了大量的模拟试验，模拟试验表明在并发的进程数大于10时，所推导的结论与模拟结果非常吻合。     

SPRINT决策树方法中I/O分析及优化研究

分析SPRINT方法的磁盘I/O,提出用读优化、写优化和磁盘文件搜索优化来减少SPRINT方法的磁盘I/O时间.读优化可使SPRINT方法省去一次读操作,写优化可以使SPRINT方法在交替层省去一次写操作,磁盘文件搜索优化可使SPRINT方法的磁盘文件搜索时间复杂性只和决策树的节点个数相关.这三种方法可单独使用,也可结合起来使用.     

Slabpose Columnsort: A New Oblivious Algorithm for Out-of-Core Sorting on Distributed-Memory Clusters

Our goal is to develop a robust out-of-core sorting program for a distributed-memory cluster. The literature contains two dominant paradigms for out-of-core sorting algorithms: merging-based and partitioning-based. We explore a third paradigm, that of oblivious algorithms. Unlike the two dominant paradigms, oblivious algorithms do not depend on the input keys and therefore lead to predetermined I/O and communication patterns in an out-of-core setting. Predetermined I/O and communication patterns facilitate overlapping I/O, communication, and computation for efficient implementation. We have developed several out-of-core sorting programs using the paradigm of oblivious algorithms. Our baseline implementation, 3-pass columnsort, was based on Leighton's columnsort algorithm. Though efficient in terms of I/O and communication, 3-pass columnsort has a restriction on the maximum problem size. As our first effort toward relaxing this restriction, we developed two implementations: subblock columnsort and M-columnsort. Both of these implementations incur substantial performance costs: subblock columnsort performs additional disk I/O, and M-columnsort needs substantial amounts of extra communication and computation. In this paper we present slabpose columnsort, a new oblivious algorithm that we have designed explicitly for the out-of-core setting. Slabpose columnsort relaxes the problem-size restriction at no extra I/O or communication cost. Experimental evidence on a Beowulf cluster shows that unlike subblock columnsort and M-columnsort, slabpose columnsort runs almost as fast as 3-pass columnsort. To the best of our knowledge, our implementations are the first out-of-core multiprocessor sorting algorithms that make no assumptions about the keys and produce output that is perfectly load balanced and in the striped order assumed by the Parallel Disk Model.