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Chapter 7 Storage

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  1. Chapter 7Storage

  2. Chapter 7 Objectives Next Explain how a compact disc stores data Differentiate between storage and memory Understand how to care for a compact disc Identify various types of storage media and storage devices Differentiate between CD-ROMs, CD-RWs, and DVD-ROMs Explain how a floppy disk stores data Identify the uses of tape Identify the advantages of using high-capacity disks Understand how an enterprise storage system works Describe how a hard disk organizes data Explain how to use PC Cards and other miniature storage media Identify the advantages of using an Internet hard drive Identify uses of microfilm and microfiche p. 7.2

  3. What is storage? The media on which data, instructions, and information are kept, as well as the devices that record and retrieve these items Memory Versus Storage Next p. 7. 2 Fig. 7-1

  4. What is memory? A temporary holding place for data and instructions Consists of one or more chips on the motherboard Sometimes called primary storage Memory Versus Storage Nonvolatile memory Does not lose its contents when power is removed from the computer Volatile memory Loses its contents when the computer’s power is turned off Most memory is volatile Next p. 7. 3

  5. How does storage differ from memory? Storage also called secondary storage, auxiliary storage, permanent storage, or mass storage Storage holds items such as data, instructions, and information for future use Storage is nonvolatile Memory Versus Storage When you are finished with the file, you remove it from memory and return it to storage When you want to work with a file, you remove it from storage and place it in memory Next p. 7. 4

  6. How does volatility compare? Memory Versus Storage Screen DisplayVolatile Contents of Memory (most RAM) Volatile Contents of Storage Nonvolatile State of Computer C6578 print cartridge$30.25 per cartridge2 cartridges$60.50 total due ON Contents of storage retained when power is off OFF Screen display and contents of most RAM (memory) erased when power is off Next p. 7. 4 Fig. 7-2

  7. What is a storage medium and a storage device? Memory Versus Storage storage device The computer hardware that records and retrieves items to and from a storage medium storage medium The physical material on which a computer keeps data, instructions, and information Next p. 7. 4

  8. What is reading and writing? Memory Versus Storage Reading Process of transferring data, instructions, and information from a storage medium into memory Serves as a source of input Writing Process of transferring items from memory to a storage medium Serves as a source of output Next p. 7. 4

  9. What is access time? The amount of time it takes the device to locate an item on a disk Defines the speed of a disk storage device Memory Versus Storage faster more expensive cost speed slower less expensive Next Memory (RAM) Hard Disk Compact Disc Floppy Disk Tape p. 7.4 Fig. 7-4

  10. What is capacity? The number of bytes (characters) a storage medium can hold Manufacturers use many terms to define the capacity of storage media Memory Versus Storage Next Storage Term Number of bytes Abbreviation Kilobyte KB 1 thousand Megabyte MB 1 million 1 billion Gigabyte GB Terabyte 1 trillion TB Petabyte PB 1 quadrillion p. 7. 4 Fig. 7-3

  11. Al Shugart Joined IBM as a customer engineer in 1951 Supervised a team in 1967 responsible for developing a removable, portable data storage device Founded Shugart Associates in 1973 and Seagate Technology in 1979 Technology Trailblazer Next Click to view Web Link then click Al Shugart p. 7.7

  12. What is a floppy disk? A portable, inexpensive storage medium Consists of a thin, circular, flexible plastic disk with a magnetic coating Enclosed in a square-shaped plastic shell Today’s standard disk is 3.5” wide Floppy Disks Next p. 7. 7

  13. What are the parts of a floppy disk? A thin circular flexible film is enclosed between two liners A piece of metal called a shutter covers an opening to the recording surface Floppy Disks liner shutter metal hub Next shell flexible thin film magnetic coating Click to view Web Link then click Floppy Disks p. 7.6 Fig. 7-5

  14. A device that can read from and write on a floppy disk Most personal computers have a floppy disk drive, in which you insert and remove a floppy disk What is a floppy disk drive (FDD)? Floppy Disks floppy disk floppy disk drive Next p. 7.7 Fig. 7-6

  15. How are floppy disk drives designated? Floppy Disks One floppy drive drive A Two floppy drives drive A drive B Next p. 7. 6

  16. How does a floppy disk store data? A type of magnetic media Uses magnetic patterns to store items such as data, instructions, and information on a disk’s surface Able to access (read) data from and place (write) data on a magnetic disk any number of times The read/write head in the floppy disk drive is the mechanism that actually reads items from or writes items on the floppy disk Floppy Disks Next p. 7. 8

  17. How does a floppy disk drive work? Floppy Disks Step 1: When you insert the floppy disk into the drive, the shutter moves to the side to expose the recording surface on the disk. Step 2: When you initiate a disk access, the circuit board on the drive sends signals to control movement of the read/write heads and the disk. Step 1 Step 2 Step 3: If disk access is a write instruction, the circuit board verifies whether the disk can be written to or not. Step 6 Step 4: A motor causes the floppy disk to spin. Step 5: A motor positions the read/write heads over the correct location on the recording surface of the disk. Step 6: The read/write heads read data from and write data on the floppy disk. Step 5 Step 4 Step 3 Next p. 7. 7 Fig. 7-7

  18. What is density? The number of bits in an area on a storage medium A floppy disk drive must support that floppy disk’s density Most floppy disks today are high density (HD) with a capacity of 1.44 MB Floppy Disks Downward compatible Able to recognize and use earlier media Floppy disk drives are downward compatible Upward compatible Able to recognize newer media Floppy disk drives are not upward compatible Next p. 7. 7

  19. What are tracks and sectors? Track: a narrow recording band that forms a full circle on the surface of the disk Pie shaped sections break the tracks into small arcs called sectors A sector can store up to 512 bytes of data A typical floppy disk stores data on both sides of the disk Floppy Disks sector18 per track track80 per side Next 80 tracks per side X 18 sectors per track X 2 sides per disk X 512 bytes per sector = 1,474,560 bytes p. 7.8 Fig. 7-8

  20. What is a cluster? The smallest unit of disk space that stores data Also called an allocation unit 2 to 8 sectors depending on the operating system Each cluster holds data from only one file One file can span many clusters Floppy Disks cluster2 to 8 sectors Next p. 7.8

  21. What is formatting? The process of preparing a disk for reading and writing Formatting marks bad sectors as unusable Floppy Disks Next p. 7. 8 Fig. 7-9

  22. How do you care for a floppy? A floppy disk can last at least seven years Proper care helps to maximize a disk’s life Floppy Disks Avoid exposure to heat and cold Avoid exposure to magnetic fields Avoid exposure to contaminants such as dust, smoke, or salt air Never open the shutter and touch the disk’s recording surface Keep disks in a storage tray when not using them Next p. 7.9

  23. What is a write-protect notch? A small opening with a cover that you slide up or down Protects floppy disks from accidentally being erased Floppy Disks notch open means you cannot write on the disk notch closed means you can write on the disk Next write-protected not write-protected p. 7. 9 Fig. 7-10

  24. What is a high-capacity disk drive? A disk drive that uses disks with capacities of 100 MB and greater High-Capacity Disks HiFD™ (High-Capacity Floppy Disk) drive Uses a 200 MB HiFD™ disk Developed by Sony Electronics, Inc. SuperDisk™ drive Uses a 120 MB or a 250 MB SuperDisk™ Developed by Imation Zip® drive Uses a Zip® disk that can store 100 MB or 250 MB of data Developed by Iomega Corporation built in Zip® drive Next Click to view Web Link then click Zip® Drives p. 7.9

  25. What is a backup? A duplicate of a file, program, or disk that you can use if the original is lost damaged, or destroyed High-capacity disks are often used to back up important data and information High-Capacity Disks instructions data information Next p. 7.9

  26. What a hard disk? Consists of several inflexible, circular platters that store items electronically Also called a hard disk drive or a fixed disk A platter is coated with a material that allows items to be recorded magnetically on its surface The components of a hard disk are enclosed in an airtight, sealed case to protect them Hard Disks Hard disk installed in system unit Next p. 7. 10 Fig. 7-12

  27. How does a hard disk work? Hard Disks Step 1: The circuit board controls the movement of the head activator and a small motor Step 2 Step 1 Step 2: A small motor spins the platters while the computer is running Step 3: When software requests a disk access, the read/write heads determine the current or new location of the data Step 4: The head actuator positions the read/write head arms over the correct location on the platters to read or write data Step 3 Step 4 Next p. 7.11 Fig. 7-13

  28. What is a cylinder? The location of a single track through all platters A single movement of the read/write head arms can read all the platters of data Hard Disks cylinder track Next Click to viewanimation p. 7. 11 Fig. 7-14

  29. What is a head crash? Occurs when a read/write head touches the surface of a platter The platters of the hard disk rotate at a high rate of speed while the computer is running The spinning creates a cushion of air that floats the read/write head above the platter Hard Disks Clearance is approximately two millionths of an inch Next hair read/write head dust smoke gap p. 7. 12 Fig. 7-15 platter

  30. How does access time compare for a hard disk and a floppy disk? A hard disk’s access time is significantly faster than a floppy disk The hard disk spins much faster than a floppy disk A hard disk spins constantly, while a floppy disk starts spinning only when it receives a read or write command Hard Disks Hard disk Approximately 5 to 11 milliseconds Floppy disk 84 milliseconds or approximately ½ a second Next Click to view Web Link then click Hard Drives p. 7. 12

  31. A portion of memory that the processor uses to store frequently accessed items What is a disk cache? Hard Disks processor processor processor disk cache disk cache disk cache hard disk hard disk hard disk first request for data — to disk cache first request for data — to disk cache Next second request for data — to hard disk • A cache controller manages cache and thus determines which items cache should store p. 7. 12 Fig. 7-16

  32. What is a partition? You can divide a formatted hard disk into separate areas called partitions Done by issuing a special operating system command Each partition functions as if it were a separate hard disk drive Hard Disks drive C Designation for first partition or for a single partition on the hard disk drive D Designation for second partition on the hard disk Next p. 7. 12

  33. What is a disk controller? A special purpose chip and associated electronic circuits that control the transfer of data, instructions, and information from a disk to the rest of the computer Sometimes called an interface A hard disk controller (HDC) is the interface for a hard disk May be part of the disk drive or a separate card inside the system unit Hard Disks USB port Used as interface for many external hard disk drives Enhanced Integrated Drive Electronics (EIDE) One of the most widely used controllers Supports up to four hard disks small computer system interface (SCSI) Supports multiple disk drives, as well as other peripherals You can daisy chain devices together Next p. 7. 13

  34. What is a removable hard disk? A disk drive in which a plastic or metal case surrounds the hard disk so you can remove it from the drive A popular, reasonably priced, removable hard disk is the Jaz® disk by Iomega Hard Disks Next p. 7. 13 Fig. 7-17

  35. Kingston Technology The world’s leading independent manufacturer of memory products of computers, servers, digital cameras, and other electronic devices Founded by John Tu and David Sun in 1987 Markets more than 2,000 products Designated as one of the 100 Best Companies to Work for in the United States by Fortune magazine Company on the Cutting Edge Next Click to view Web Link then click Kingston Click to view video p. 7. 13

  36. What is RAID? Redundant array of independent disks A type of hard disk system that connects several smaller disks into a single unit that acts like a single large hard disk More reliable than a traditional disk system but quite expensive Hard Disks Next p. 7.14 Fig. 7-18

  37. How does RAID work? RAID duplicates data, instructions, and information to improve data reliability Hard Disks Mirroring(RAID Level 1) Striping Next • Level 1, called mirroring, has one backup disk for each disk • Levels beyond level 1 use a technique called striping, which splits data, instructions, and information across multiple disks in the array p. 7. 14 Fig. 7-19

  38. Windows provides many maintenance and monitoring utilities for a hard disk on the System Tools submenu What utilities maintain a hard disk drive? Hard Disks Next Click to view Web Link then click Utilities p. 7. 15 Fig. 7-20

  39. What is an Internet hard drive? A service on the Web that provides storage to computer users Sometimes called online storage Many offer storage free of charge Revenues come from advertisers Hard Disks Next p. 7. 16 Fig. 7-21

  40. What are advantages of an Internet hard drive? Hard Disks Large audio, video, and graphics files can be downloaded to an Internet hard drive instantaneously Files can be accessed from any computer or device that has Web access Others can be authorized to access data from your Internet hard drive Allows offsite backups of data Next p. 7. 16

  41. What is a compact disc (CD)? A flat, round, portable, metal storage medium that usually is 4.75 inches in diameter and less than one-twentieth of an inch thick Most personal computers today include some type of compactdisc drive Also called an optical disc Available in a variety of formats Compact Discs Next CD-ROM CD-RW CD-R DVD-ROM p. 7. 17

  42. How do you use a compact disc? CD drives can read compact discs, including audio discs Most CD drives include a volume control button and a headphone jack The drive designation of a CD drive usually follows alphabetically after that of the hard disk Compact Discs Insert disc, label side up Push button to slide out the tray Next Push the same button to close the tray p. 7. 17 Fig. 7-22

  43. How does a laser read data on a compact disc? Items are stored using microscopic pits (indentations) and land (flat areas) that are in the middle layer of the disk A laser light reads items from the compact disc Compact Discs Compact disc label Compact disc label Compact disc label Compact disc label Compact disc label Step 3 Step 2 Step 1 pit pit land land lens lens lens lens lens lens lens lens 0 1 prism prism prism prism prism prism prism prism Light-sensing diode Light-sensing diode laser diode laser diode laser diode laser diode laser diode laser diode laser diode laser diode Next Step 2: If light strikes a pit, it scatters. If light strikes land, it is reflected back toward the laser diode. Step 1: A laser diode shines a light beam toward the compact disc. Step 3: Reflected light is deflected to a light-sensing diode, which sends digital signals of 1 to the computer. Absence of reflected light is read as a digital signal of 0. p. 7. 18 Fig. 7-23

  44. How is data stored on a compact disc? A compact disc typically stores items in a single track It spirals from the center of the disc to the edge of the disc The track is divided into evenly sized sectors in which items are stored Compact Discs Single track spirals to edge of disc Next Compact disc sectors p. 7. 18 Fig. 7-24

  45. What is a jewel box? A protective case for a compact disc Place a compact disc in a jewel box to protect data Compact Discs Next p. 7.19 Fig. 7-25

  46. How should you care for a compact disc? Compact Discs Next 1: Do not expose the disc to excessive heat or sunlight. 2: Do not eat, smoke, or drink near a disc. 3: Do not stack discs. 4: Do not touch the underside of the disc. 5: Do store the disc in a jewel box when not in use. 6: Do hold a disc by its edges. p. 7.19 Fig. 7-26

  47. What is a CD-ROM? A silver-colored compact disc that uses the same laser technology as audio CDs for recording music Can contain text, graphics, audio, and video The manufacturer writes, or records, the contents of standard CD-ROMs You cannot erase or modify the contents A CD-ROM drive or CD-ROM player is used to read items on a CD-ROM CD-ROMs Next p. 7. 20

  48. What is the storage capacity of a CD-ROM? A typical CD-ROM holds about 650 MB of data, instructions, and information Manufactures use CD-ROMs to store and distribute today’s multimedia and other complex software CD-ROMs Next Click to view Web Link then click CD-ROMs p. 7. 20 Fig. 7-27

  49. What is the data transfer rate of a CD-ROM drive? The time it takes a drive to transmit data, instructions, and information from the drive to another device Slower CD-ROM drives produce choppy images or sound Drive speed measured relative to original CD-ROM drives (150 KB per second) CD-ROMs 40X 40 X 150 KB per second = 6,000 KB per second or 6 MB per second 75X 75 X 150 KB per second = 12,250 KB per second or 12.25 MB per second Next range of current rates p. 7.20

  50. What is a PhotoCD? A compact disc that contains digital photographic images saved in the PhotoCD format Based on a file format developed by Eastman Kodak Used by commercial and professional users CD-ROMs Next • A multisession disc, which means you can write additional data, instructions, and information to the disc at a later time p. 7. 21 Fig. 7-28