DOCSLIB.ORG

Secondary Memory

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Secondary Memory Secondary Memory Memory Hierarchy: In modern computers, there are several types of memory: • Cache: RAM technology Capacity 256K- 1 M, 10 nanoseconds • Main memory: RAM - ROM technology 100 M- 1G, 100 nanoseconds • Secondary storage (Disk): 10 G-1000 G, 10-30 milliseconds • Tertiary Storage (Tape, CD):1G -100 T, a few seconds- a few minutes The memory system in a computer is organized as a hierarchy containing faster, more expensive members and slower, less expensive members. CPU cache Main Disk Tape memory Memor Memory Memory y Components towards the left side, which are nearer of the CPU, need faster access times and thus are more expensive. Components on the right side provide slower access times, but cost less. Information must flow back and forth in the hierarchy. Magnetic Disks: - Bits of data (0’s and 1’s) are stored on circular magnetic platters called disks - A disk rotates rapidly - A disk head reads and writes bits of data as they pass under the head - Often several platters are organized into a disk pack - Disks are non-volatile, stable - They have tremendous capacity (about 100 times more than RAM) - They are much cheaper than RAM (40 times cheaper per Meg) Disk Organization: - Disks are direct access storage devices as opposed to serial devices (tapes) - Disks are composed of a disk assembly and a head assembly - A disk assembly is a collection of one or more platters with a common spindle (axle) - Information is stored in the surface of the platters. - A head assembly consists of several disk arms ending in disk heads. - The arm can move outwards or inwards towards the spindle read/write head (1 per surface) Surface1 Surface 2 Surface 3 moving arm Surface 4 (starts and stops) Surface 5 Surface 6 spindle (rotating shaft never stops) 3 platters, 6 surfaces, 6 read/write heads Organization of data on the surface of the platter: Track Sector (wedge) Block (sequence of bits) Each platter surface is divided into tracks (concentric circles). Tracks above and below one another form a cylinder Each track is divided into sectors; a sector is the smallest addressable unit. Each block of data is addressed by its track, sector, and surface: track 126, sector 4, surface 3. Given the address of a block, the disk head moves to the given track, and waits for the block to rotate into position. This process takes a long time, but once in position, the block rotates under past the head very quickly. Consequently, it takes a long time to read the first bit in a block, but very little time to read the remaining bits in the block. For this reason, a disk reads/writes an entire block of data at a time, not just a single bit or byte. Typically, only one head can read/write at a given time. All heads move together, they are all at the same radius. Cylinders: A cylinder is the set of tracks at a given radius of a disk pack. A cylinder is the set of tracks that can be accessed without moving the disk arm. Moving the disk arm is relatively slow. Once the heads are positioned at a cylinder, data in that cylinder can be accessed more quickly than data in other cylinders. We try to store related data (e.g. a file) on the same cylinder. Access Time: - Given the address of a block, it takes time to access (read or write) it. - Access time has two main components: a. Seek time: the time needed to move the read/write heads to the correct track. It is the most expensive time, since it is mechanical o It takes 5 ms (milliseconds) to move from one track to the next (track-to-track) o 50 ms maximum (from inside track to outside track) o 10 to 30 ms average (from one random track to another random track) o Average seek time: about 1/3 of the total number of cylinders b. Latency (rotational delay): It is the time needed for the desired bit to rotate into position under the disk head, typically the value of latency is 8 ms Note: - Min latency =0 - Max latency = Time for disk revolution - Average latency= Min +Max/2 OR Max/2 OR time for ½ disk revolution - Most disks today rotate at least at 5000-9000 rpm, which is about 6-11 milliseconds per revolution. c. Transfer time is calculated as follows: (number of bytes transferred/number of bytes on track )*rotation time. Transfer time for a 4K block is about half a millisecond. Example: Given the following disk characteristics: - 20 surfaces - 25 sectors/ surface - 800 tracks / surface - 512 bytes / block - 3600 rpm (revolutions per minute) - 7 ms track-to-track seek time. - 28 ms avg seek time - 50 ms max seek time Latency: 3600 rpm Î 3600 rev/min Î3600/60 =60 rev/sec Î 1/60 sec/rev Î .0167 sec/rev Î 16.7 ms max latency Î 16.7/2 = 8.35 ms avg latency Disk Capacity 20 surfaces 25 sectors 800 tracks 512 Bytes/block #bytes/track = #bytes/block * # blocks/track = 512 *25 = 12,800 Bytes= 12.8 KB #Bytes/surface = # bytes/track * # tracks/surface = 12,800 * 800 = 10,240,00 Bytes = 10.24 MB (mega Bytes) #Bytes/pack = #bytes/surface * #surfaces/pack = 10.24 MB * 20 = 204.8 MB Read Time (Cylinder by Cylinder) How long does it take to read the entire disk, one cylinder at a time - 20 surfaces - 25 sectors/ surface - 800 tracks / surface - 512 bytes / block - 3600 rpm (revolutions per minute) - 7 ms track-to-track seek time. - 28 ms avg seek time - 50 ms max seek time Track latency = 16.7 ms (1 revolution) surface latency = track latency x #tracks/surface = 16.7 ms * 800 = 13360ms= 13.36s Total read time= surface latency * #surfaces + #track switches * track-to-track seek time = 13360*20 + 799*7 = Total Read time = 800 cylinder reads + 799 cylinder switches Total read time = 800 cylinder reads + 799 cylinder switches 14244 4344 14244 4344 totat latency total seek−time Total read time = (800 *334 ms) + (799 * 7 ms) = 267 sec + 5.59 sec = 272.59 sec Observation: read-time per byte = Total read time /# bytes/pack = 273 sec/204.8 MB = 1.33 sec/MB = 1.33 µs/byte (micro sec/byte) This is comparable to main memory speed! Reading a disk sequentially is very fast. In contrast, seek time for a random read of 1 byte is 28 ms, i.e., 28,000 µs. Data processing requires random access. Usually, we do not read more than one block (512 bytes) sequentially at any given time, i.e., Read a block, while processing it. .
Load more

Recommended publications
  • Hp Storageworks Disk System 2405
    user’s guide hp StorageWorks disk system 2405 Edition E0902 . Notice Trademark Information © Hewlett-Packard Company, 2002. All rights Red Hat is a registered trademark of Red Hat Co. reserved. C.A. UniCenter TNG is a registered trademark of A6250-96020 Computer Associates International, Inc. Hewlett-Packard Company makes no warranty of Microsoft, Windows NT, and Windows 2000 are any kind with regard to this material, including, but registered trademarks of Microsoft Corporation not limited to, the implied warranties of HP, HP-UX are registered trademarks of Hewlett- merchantability and fitness for a particular purpose. Packard Company. Command View, Secure Hewlett-Packard shall not be liable for errors Manager, Business Copy, Auto Path, Smart Plug- contained herein or for incidental or consequential Ins are trademarks of Hewlett-Packard Company damages in connection with the furnishing, performance, or use of this material. Adobe and Acrobat are trademarks of Adobe Systems Inc. This document contains proprietary information, which is protected by copyright. No part of this Java and Java Virtual Machine are trademarks of document may be photocopied, reproduced, or Sun Microsystems Inc. translated into another language without the prior NetWare is a trademark of Novell, Inc. written consent of Hewlett-Packard. The information contained in this document is subject to AIX is a registered trademark of International change without notice. Business Machines, Inc. Tru64 and OpenVMS are registered trademarks of Format Conventions Compaq Corporation.
    [Show full text]
  • Computer Peripheral Memory System Forecast
    OF NBS H^^LK,!,, STAND S. TECH PUBLICATIONS | COMPUTER SUici^CZ^i TECHNOLOGY: COMPUTER PERIPHERAL MEMORY SYSTEM FORECAST QC 100 U57 NBS Special Publication 500-45 #500-45 U.S. DEPARTMENT OF COMMERCE 1979 National Bureau of Standards NATIONAL BUREAU OF STANDARDS The National Bureau of Standards' was established by an act of Congress March 3, 1901 . The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is performed by the National Measurement Laboratory, the National Engineering Laboratory, and the Institute for Computer Sciences and Technology. THE NATIONAL MEASUREMENT LABORATORY provides the national system of physical and chemical and materials measurement; coordinates the system with measurement systems of other nations and furnishes essential services leading to accurate and uniform physical and chemical measurement throughout the Nation's scientific community, industry, and commerce; conducts materials research leading to improved methods of measurement, standards, and data on the properties of materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government Agencies; develops, produces, and distributes Standard Reference Materials; and provides calibration services. The Laboratory consists of the following centers: Absolute Physical Quantities^ — Radiation Research — Thermodynamics and Molecular Science — Analytical Chemistry — Materials Science.
    [Show full text]
  • The Innovator's Dilemma
    Part One WHY GREAT COMPANIES CAN FAIL CHAPTER ONE How Can Great Firms Fail? Insights from the Hard Disk Drive Industry When I began my search for an answer to the puzzle of why the best firms can fail, a friend offered some sage advice. “Those who study genetics avoid studying humans,” he noted. “Because new generations come along only every thirty years or so, it takes a long time to understand the cause and effect of any changes. Instead, they study fruit flies, because they are conceived, born, mature, and die all within a single day. If you want to understand why something happens in business, study the disk drive industry. Those companies are the closest things to fruit flies that the business world will ever see.” Indeed, nowhere in the history of business has there been an industry like disk drives, where changes in technology, market structure, global scope, and vertical integration have been so pervasive, rapid, and unrelenting. While this pace and complexity might be a nightmare for managers, my friend was right about its being fertile ground for research. Few industries offer researchers the same opportunities for developing theories about how different types of change cause certain types of firms to succeed or fail or for testing those theories as the industry repeats its cycles of change. This chapter summarizes the history of the disk drive industry in all its complexity. Some readers will be interested in it for the sake of history itself.1 But the value of understanding this history is that out of its complexity emerge a few stunningly simple and consistent factors that have repeatedly determined the success and failure of the industry’s best firms.
    [Show full text]
  • Sperry Univac 11 00/80 System
    70C-877-14a Computers Sperry Univac 11 00/80 System MANAGEMENT SUMMARY The 1100/80 is a large-scale computer system available in a number of different First delivered in 1977, the 1100/80 is the middle member of the currently active 1100 Series family of large-scale configurations. The system can perform computer systems. In terms of performance, the 1100/80 effectively in a broad range of applications, including batch and interactive processing, fits between the smaller 1100/60 (Report 70C-877-12) and the top-of-the-line 1100/90 (Report 70C-877-16). The engineering/scientific applications, and 1100/80 is upwardly compatible with the 1100/90 and business data processing. supports the same peripqeral devices and the same software. MODELS: 1100/80, 1100/81, 1100/82, 1100/83, and 1100/84. The 1100/80 also supports the Array Processor Subsystem CONFIGURATION: From 512K to 8192K (APS), a powerful "number cruncher" designed for high­ words of main memory, from 1 to 4 CPUs, volume mathematical applications. Thus far, the APS is and from 4 to 104 I/O channels. available for the 1100/80 only. COMPETITION: Burroughs B 6800/7800, Honeywell DPS 8, IBM 303X Series. PRICE: Purchase prices range from PROCESSORS $1,389,628 to $6,128,808. All 1100/80 systems are based on the same 50-nanosecond central processor. Featuring multi-layer printed circuit CHARACTERISTICS boards, emitter-coupled logic (ECL), and a buffer memory, the 1100/80 systems can have up to 8 million MANU~ACTURER: Sperry Univac Division, Sperry Corporation, P.O. Box 500, Blue Bell, Pennsylvania 19424.
    [Show full text]
  • Hard Disk Drive Specifications Models: 2R015H1 & 2R010H1
    Hard Disk Drive Specifications Models: 2R015H1 & 2R010H1 P/N:1525/rev. A This publication could include technical inaccuracies or typographical errors. Changes are periodically made to the information herein – which will be incorporated in revised editions of the publication. Maxtor may make changes or improvements in the product(s) described in this publication at any time and without notice. Copyright © 2001 Maxtor Corporation. All rights reserved. Maxtor®, MaxFax® and No Quibble Service® are registered trademarks of Maxtor Corporation. Other brands or products are trademarks or registered trademarks of their respective holders. Corporate Headquarters 510 Cottonwood Drive Milpitas, California 95035 Tel: 408-432-1700 Fax: 408-432-4510 Research and Development Center 2190 Miller Drive Longmont, Colorado 80501 Tel: 303-651-6000 Fax: 303-678-2165 Before You Begin Thank you for your interest in Maxtor hard drives. This manual provides technical information for OEM engineers and systems integrators regarding the installation and use of Maxtor hard drives. Drive repair should be performed only at an authorized repair center. For repair information, contact the Maxtor Customer Service Center at 800- 2MAXTOR or 408-922-2085. Before unpacking the hard drive, please review Sections 1 through 4. CAUTION Maxtor hard drives are precision products. Failure to follow these precautions and guidelines outlined here may lead to product failure, damage and invalidation of all warranties. 1 BEFORE unpacking or handling a drive, take all proper electro-static discharge (ESD) precautions, including personnel and equipment grounding. Stand-alone drives are sensitive to ESD damage. 2 BEFORE removing drives from their packing material, allow them to reach room temperature.
    [Show full text]
  • Formatting a Disk
    System Administration Guide: Devices and File Systems Part No: E37385–02 June 2013 Copyright © 2004, 2013, Oracle and/or its affiliates. All rights reserved. This software and related documentation are provided under a license agreement containing restrictions on use and disclosure and are protected by intellectual property laws. Except as expressly permitted in your license agreement or allowed by law, you may not use, copy, reproduce, translate, broadcast, modify, license, transmit, distribute, exhibit, perform, publish, or display any part, in any form, or by any means. Reverse engineering, disassembly, or decompilation of this software, unless required by law for interoperability, is prohibited. The information contained herein is subject to change without notice and is not warranted to be error-free. If you find any errors, please report them to us in writing. If this is software or related documentation that is delivered to the U.S. Government or anyone licensing it on behalf of the U.S. Government, the following notice is applicable: U.S. GOVERNMENT END USERS. Oracle programs, including any operating system, integrated software, any programs installed on the hardware, and/or documentation, delivered to U.S. Government end users are "commercial computer software" pursuant to the applicable Federal Acquisition Regulation and agency-specific supplemental regulations. As such, use, duplication, disclosure, modification, and adaptation of the programs, including anyoperating system, integrated software, any programs installed on the hardware, and/or documentation, shall be subject to license terms and license restrictions applicable to the programs. No other rights are granted to the U.S. Government. This software or hardware is developed for general use in a variety of information management applications.
    [Show full text]
  • 1. Types of Computers Contents
    1. Types of Computers Contents 1 Classes of computers 1 1.1 Classes by size ............................................. 1 1.1.1 Microcomputers (personal computers) ............................ 1 1.1.2 Minicomputers (midrange computers) ............................ 1 1.1.3 Mainframe computers ..................................... 1 1.1.4 Supercomputers ........................................ 1 1.2 Classes by function .......................................... 2 1.2.1 Servers ............................................ 2 1.2.2 Workstations ......................................... 2 1.2.3 Information appliances .................................... 2 1.2.4 Embedded computers ..................................... 2 1.3 See also ................................................ 2 1.4 References .............................................. 2 1.5 External links ............................................. 2 2 List of computer size categories 3 2.1 Supercomputers ............................................ 3 2.2 Mainframe computers ........................................ 3 2.3 Minicomputers ............................................ 3 2.4 Microcomputers ........................................... 3 2.5 Mobile computers ........................................... 3 2.6 Others ................................................. 4 2.7 Distinctive marks ........................................... 4 2.8 Categories ............................................... 4 2.9 See also ................................................ 4 2.10 References
    [Show full text]
  • Storage Hardware DVD ROM/RW
    University of Dublin Hardware Issues Trinity College Hard Disk Main Memory CD ROM/RW CPU Cache Storage Hardware DVD ROM/RW Tapes [email protected] Primary Storage Floppy Disk Secondary Storage Storage Hardware 2 Hardware Issues Hardware Issues Primary Storage is … Secondary Storage is … • Limited • Extendible •Volatile • Persistent • Expensive • Cheap However, it is also … However, it is … • Fast (May be accessed directly from the CPU) • Relatively slow (must be copied to main memory before being accessed by the CPU) Storage Hardware 3 Storage Hardware 4 Hardware Issues Disk Storage Devices Why do we use secondary storage? Disk Storage Devices … • Primary storage (RAM) costs more than disk space • Direct Access Storage • We like to switch our computers off and on again – As opposed to Tape drives, which are serial devices • Offer high storage capacity and low cost • Data stored as magnetized areas on magnetic platters But secondary storage is very slow surfaces • Each disk has one or more platters • Retrieving a single character from RAM takes about 150 •A disk pack contains several magnetic platters connected nanoseconds (150 billionths of a second) to a rotating spindle • Retrieving the same character from disk takes about 75 milliseconds (thousandths of a second) • 75 msec is 500,000 times longer than 150 ns. Storage Hardware 5 Storage Hardware 6 1 Disk Pack with Read/Write H/W Movable vs Fixed-head Disks Spindle Some disks have fixed-heads Arm Read/Write Head Cylinder of Actuator Tracks (imaginary) • As many read/write heads as
    [Show full text]
  • A PERSPECTIVE on the FUTURE of the MAGNETIC HARD DISK DRIVE (HDD) TECHNOLOGY Rajat Chaudhary1, Archika Kansal2 1Asst
    International Journal of Technical Research and Applications e-ISSN: 2320-8163, www.ijtra.com Volume 3, Issue 3 (May-June 2015), PP. 63-74 A PERSPECTIVE ON THE FUTURE OF THE MAGNETIC HARD DISK DRIVE (HDD) TECHNOLOGY Rajat Chaudhary1, Archika Kansal2 1Asst. Professor, Department of Information Technology, Bharat Institute of Technology, Meerut 2Department of Information Technology [email protected], [email protected] Abstract- It is estimated that over 80% of all new modern era of servers and personal computers. More than information produced in the world is being stored on storage 200 companies have produced HDD units, though most devices such as pen-drive, storage chips or magnetic media, but current units are manufactured by Seagate, Toshiba and most of it on hard disk drives. This paper presents a detailed Western Digital. Figure below is an example of the Hard introduction of the working, components and logical operations Disk Drive. of storage device especially we focuses on the magnetic disk drive i.e. Hard Disk. In addition to presenting failure statistics, we analyze the correlation between failures and several parameters generally believed to impact longevity. Our analysis identifies several parameters from the drive’s self monitoring facility (SMART) that correlate highly with failures. Despite this high correlation, we conclude that models based on SMART parameters alone are unlikely to be useful for predicting individual drive failures. Finally, future of information storage is examined, and storage technologies toward 1TB recording are investigated and discuss about how can we increase the performance in the hard disk drive. Index Terms— HDD, SSD, Magneto-resistive head, Platters, Actuator, Spindle, Voice Coil, SATA, Skyrmions.
    [Show full text]
  • Personal Computer for Disabling Resume Mode Upon Replacement of HDD
    Europaisches Patentamt J) European Patent Office (") Publication number: 0 426 1 33 A2 Office europeen des brevets EUROPEAN PATENT APPLICATION © Application number: 90120837.1 © int. ci.5: G06F 3/06 © Date of filing: 30.10.90 © Priority: 31.10.89 JP 281738/89 © Applicant: Kabushiki Kaisha Toshiba 72, Horikawa-cho Saiwai-ku @ Date of publication of application: Kawasaki-shi(JP) 08.05.91 Bulletin 91/19 @ Inventor: Hibi, Kenji, c/o Intellectual Property ® Designated Contracting States: Division DE FR GB Kabushiki Kaisha Toshiba, 1-1 Shibaura 1-chome Minato-ku, Tokyo 105(JP) © Representative: Henkel, Feiler, Hanzel & Partner Mohlstrasse 37 W-8000 MUnchen 80(DE) © Personal computer for disabling resume mode upon replacement of HDD. © When a hard disk pack (20) is removed from a F/F (67) that the hard disk pack (20) has been computer main body in a power-OFF state, a signal replaced. The CPU (11) disables a resume flag. As a level of a specific pin of a connector (61) is set at result, upon a power-ON operation, resume process- high level, and a signal of high level representing ing is not performed, and damage to the hard disk replacement of the hard disk pack (20) is set in a pack and overrun of a program can be prevented. flip-flop (F/F) 67. When a power switch is turned on, a CPU (11) determines from information set in the + 5V :/71 HDCHG SIGNAL C4 < 73 CO CO 20 CLEAR SIGNAL Q- 111 F I G. 3 Xerox Copy Centre EP 0 426 133 A2 PERSONAL COMPUTER FOR DISABLING RESUME MODE UPON REPLACEMENT OF HDD The present invention relates to a personal puter having a detachable disk unit and a resume computer using a replaceable hard disk as an function, comprises the computer steps of: a) de- external storage medium.
    [Show full text]
  • Timeline of Computer History
    Timeline of Computer History By Year By Category Search AI & Robotics (55) Computers (145) Graphics & Games (48) Memory & Storage (61)(61) Networking & The Popular Culture (50) Software & Languages (60) Manchester Mark I Williams- 1947 Kilburn tube EDSAC 1949 Manchester Mark I Williams-Kilburn tube At Manchester University, Freddie Williams and Tom Kilburn develop the Williams-Kilburn tube. The tube, tested in 1947, was the first high-speed, entirely electronic memory. It used a cathode ray tube (similar to an analog TV picture tube) to store bits as dots on the screen’s surface. Each dot lasted a fraction of a second before fading so the information was constantly refreshed. Information was read by a metal pickup plate that would detect a change in electrical charge. Maurice Wilkes with EDSAC Maurice Wilkes and his team at the University of Cambrid construct the Electronic Delay Storage Automatic Calcula (EDSAC). EDSAC, a stored program computer, used me delay line memory. Wilkes had attended the University of Pennsylvania's Moore School of Engineering summer sessions about the ENIAC in 1946 and shortly thereafter Magnetic drum memory began work on the EDSAC. 1950 MIT - Magnetic core memory ERA founders with various magnetic drum memories Eager to enhance America’s codebreaking capabilities, the US Navy contracts with Engineering Research Associates (ERA) for a stored program computer. The result was Atlas, completed in 1950. Atlas used magnetic drum memory, which stored information on the outside of a rotating cylinder coated with ferromagnetic material and circled by read/write heads in Jay Forrester holding early core memory plane fixed positions.
    [Show full text]
  • Memory Organisation
    MEMORY ORGANISATION Structure 3.0 Introduction 3.1 Objectives 3.2 Memory System 3.3 Characteristics Terms for Various Memory Devices 3.4 Random Access Memory 3.4.1 .Ferrite Core Memories 3.4.2 Se~niconductorMemories 3.4.3 Read Only Me~nories 3.4.4 Chip Organisation 3.5 External/Auxiliary Memory 3.5.1 Magnetic Disk 3 .5.2 Magnetic Tapes 3.5.3 Charge-Coupled Devices (CCDs) 3.5.4 Magnetic Bubble Memories 3.5.5 Optical Me~nories 3.6 High Speed Me~nories 3.6.1 Interleaved Me~nories 3.6.2 Cache Memory 3.6.3 Associative Me~nories 3.7 Summary 3.8 Model Answers 3.0 INTRODUCTION We have already discussed, in unit 1, about tlie basic computer structure. We had started our discussions, in the previous unit, with tlie digital logic circuits, the basic building block of modern computers and then moved on to: discuss one of tlie most important interconnection structure the Bus structure of the computer. The other basic components of a computer should now be discussed to make the picture complete. We can start with CPU structure and go on to discuss memory, input/output etc., but for the sake of simplicity we will start with lnemory organisation and then move on to Input/Output organisation (Unit 4) and then we will devote a full block on CPU i organisation (Block 2). In this unit we will discuss about the main memory, cache memory, magnetic secondary memory, optical memory. With the advancement of technologies tlie optical memories are becoming increasingly popular and, therefore, will be discussed in sufficient details in the unit.
    [Show full text]