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Ch.13 Secondary Storage Devices

Ch.13 Secondary Storage Devices. S4C Catherine Cho Red Yeung Jessica Tsang. 13.1 Secondary Storage Devices. Also called “Backing storage” Store data, operating system and application software Non-volatile Measured by access time and data transfer rate

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Ch.13 Secondary Storage Devices

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  1. Ch.13 Secondary Storage Devices S4C Catherine Cho Red Yeung Jessica Tsang

  2. 13.1 Secondary Storage Devices • Also called “Backing storage” • Store data, operating system and application software • Non-volatile • Measured by access time and data transfer rate • Can be classified into 2 main types • Magnetic storage devices • Optical storage devices

  3. Secondary storage device CPU Main Memory

  4. The Speed of a Secondary Storage Device Data transfer rate Searching speed Reading/writing process Access time

  5. Storage Capacity

  6. Different Concept of Magnetic Storage Device and Optical Storage Devices

  7. 13.2 Magnetic Storage Devices • Most of them read/write enabled • E.g. floppy disks, hard disks, magnetic tapes

  8. Floppy Disks • Only have 1.44 MB • Usually used for backing up and transferring a small amount of data • Direct access mode

  9. Advantages and Disadvantages of the Floppy Disks

  10. Hard Disks • Have one or more circular disks • Called platters • Each platters have a large number of tracks • Direct access mode • Fast, durable, high-capacity storage medium

  11. The time of access data file The data transfer rate The rotational speed The speed rotations of disk plates The time of access data file The movement of read/write heads

  12. Magnetic Tapes • Sequential access mode • For back up purpose • Latest magnetic type = DAT • Storage over 72GB • Low cost

  13. 13.3 Optical Storage Devices • Most of them --> store data, instructions • E.g CD-Rom, CD-R, DVD ,DVD-R

  14. Compact Disc Read-Only Memory (CD-ROM) • Data stores and accesses by via red laser • The content --> permanently • Data represented by pits and lands

  15. The mechanism of a CD-ROM drive P.78 PICTURE

  16. CD-ROM drive • The speed --> its data transfer rate • direct proportion • Measured relative to use 2x, 4x, 8x, etc • To describe the speeds

  17. CD-R and CD-RW • Both CD-R drives and CD-RW drives • Allow to write data • CD-RW can rewrite data many times over

  18. Digital Versatile Disc (DVD) • Store up to 17GB of Data • Can saved movies and libraries of multimedia files • Many different variations • DVD+R, DVD-R, DVD+RW, DVD-RW, DVD-RAM • The concept of write data on to DVD same with a floppy disk • To copy, modify and delete files • The speed to write over 8x

  19. Different types of drives

  20. High-definition digital versatile disc (HD DVD) and Blu-ray Disc • For storing digital media • Used the blue-violet laser technology • Are incompatible

  21. Storage capacities of different types of drives

  22. The data transfer speed of different types of drives

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