Storage devices


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Storage devices

  1. 1. Lecture # 511/21/2012 Designed by Prof. Anosha Khan 1
  2. 2.  Storage devices hold data, even when the computer is turned off.  The physical material that actually holds data is called a storage medium. The surface of a floppy disk is a storage medium.  The hardware that writes data to or reads data from a storage medium is called a storage device. A floppy disk drive is a storage device.  The two primary storage technologies are magnetic and optical.11/21/2012 Designed by Prof. Anosha Khan 2
  3. 3. 11/21/2012 Designed by Prof. Anosha Khan 3
  4. 4.  Surface of magnetic Disks and tapes are coated with millions of tiny iron particles so that data can be stored on them Read/Write heads of a magnetic disk or tape drive contains electromagnets that generate magnetic fields in the iron on the storage medium as the head passes over the disk11/21/2012 Designed by Prof. Anosha Khan 4
  5. 5.  A storage device is the computer hardware that records and/or retrieves items to and from storage media Reading is the process of transferring items from a storage medium into memory Writing is the process of transferring items from memory to a storage medium11/21/2012 Designed by Prof. Anosha Khan 5
  6. 6.  Access time measures:  The amount of time it takes a storage device to locate an item on a storage medium  The time required to deliver an item from memory to the processor 11/21/2012 Designed by Prof. Anosha Khan 6
  7. 7.  Formatting is the process of dividing the disk into tracks and sectors so that the operating system can store and locate data and information on the disk Before a magnetic disk can be used, it must be formatted— a process that maps the disks surface and determines how data will be stored. During formatting, the drive creates circular tracks around the disks surface, then divides each track into sectors. The OS organizes sectors into groups, called clusters, then tracks each files location according to the clusters it occupies. 11/21/2012 Designed by Prof. Anosha Khan 7
  8. 8.  Boot sector File allocation Table (FAT) Root folder Data Area11/21/2012 Designed by Prof. Anosha Khan 8
  9. 9.  Tracks-  circular areas of the disk  Length of a track one circumference of disk  Over 1000 on a hard disk  Data first written to outer most track Sectors-  Divides tracks sections  On a floppy 9 sectors exits11/21/2012 Designed by Prof. Anosha Khan 9
  10. 10.  Cylinders-  Logical groupings of the the same track on each disk surface in a disk unit Clusters-  Groups of sectors used by operating system  64 sectors in one cluster Partitioning: divide hard disk into separate areas called partitions; each partition functions as if it were a separate hard disk drive.11/21/2012 Designed by Prof. Anosha Khan 10
  11. 11.  File Allocation Table(FAT) FAT32 New Technology file system (NTFS) NTFS 5 High performance File System (HPFS)11/21/2012 Designed by Prof. Anosha Khan 11
  12. 12.  Uses magnetic storage technology Has read / write heads Includes a motor that rotates the disk on a spindle and read/ write head that can move to any spot on the disk’s surface as the disk spins Disk Density- the amount of data that a disk can hold To determine disk density multiply its total number of sectors by the number of bytes each sector can hold11/21/2012 Designed by Prof. Anosha Khan 12
  13. 13.  Hard disks can store data using longitudinal recording or perpendicular recording Includes one or more platters mounted on a central spindle Each platter is covered with a magnetic coating It includes motor to spin platters and read/write heads11/21/2012 Designed by Prof. Anosha Khan 13
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  15. 15.  An external hard disk is a separate free- standing hard disk that connects to your computer with a cable or wirelessly A removable hard disk is a hard disk that you insert and remove from a drive11/21/2012 Designed by Prof. Anosha Khan 15
  16. 16.  Tape is a magnetically coated ribbon of plastic capable of storing large amounts of data and information A tape drive reads and writes data and information on a tape11/21/2012 Designed by Prof. Anosha Khan 16
  17. 17.  An optical disc consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser An optical disk is a high-capacity storage medium. An optical drive uses reflected light to read data. To store data, the disks metal surface is covered with tiny dents (pits) and flat spots (lands), which cause light to be reflected differently. When an optical drive shines light into a pit, the light cannot be reflected back. This represents a bit value of 0 (off). A land reflects light back to its source, representing a bit value of 1 (on).11/21/2012 Designed by Prof. Anosha Khan 17
  18. 18.  A magnetic stripe card contains a magnetic stripe that stores information A smart card stores data on a thin microprocessor embedded in the card11/21/2012 Designed by Prof. Anosha Khan 18
  19. 19.  A CD-Recordable (CD-R) drive lets you record your own CDs, but data cannot be overwritten once it is recorded to the disk. A CD-Rewritable (CD-RW) drive lets you record a CD, then write new data over the already recorded data. PhotoCD technology is used to store digital photographs. DVD recordable11/21/2012 Designed by Prof. Anosha Khan 19
  20. 20.  Flash memory Smart Cards11/21/2012 Designed by Prof. Anosha Khan 20
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