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Hard Drive vs. Floppy Drive

Hard Drive vs. Floppy Drive. Start with a non-magnetic platter. Floppy Disk - Mylar Hard Disk - Metal, Ceramic, or Glass. 2. Coat with a thin layer of magnetic material. 3. Two important characteristics of the magnetic surface:. Coercivity Retentivity. Coercivity.

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Hard Drive vs. Floppy Drive

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  1. Hard Drive vs. Floppy Drive

  2. Start with a non-magnetic platter. Floppy Disk - Mylar Hard Disk - Metal, Ceramic, or Glass 2

  3. Coat with a thin layer of magnetic material. 3

  4. Two important characteristics of the magnetic surface: • Coercivity • Retentivity

  5. Coercivity • How strongly the material resists changing its magnetic field. • Must be high enough to resist changes by unintentional means. • Must be low enough so that excess write current is not required. • Generally, larger drive capacities require higher coercivity.

  6. Retentivity • How well the magnetic material retains its magnetic field. • Relates to how long a magnetic material can retain data without degradation.

  7. Magnetic domains randomly arranged. (Blank media) 7

  8. Pick-up device - Read/Write Head 8

  9. Magnetic domains orderly arranged. (Recorded Media) 9

  10. Reading Data from the Disk. 10

  11. Writing Data on a Blank Disk. 11

  12. 12

  13. The disk surface is divided into tracks. 13

  14. Track 79 Track 1 Track 0 14

  15. Side 1, Track 0 Side 2, Track 0 15

  16. Read\Write Head Disk Read\Write Head 16

  17. One Sector = 512 Bytes 17

  18. SECTOR • The smallest unit of storage on a disk. • 512 bytes or 0.5 kbytes • Grouped into clusters

  19. Double-sided, double-density (DSDD) 5¼" Floppy Disk • 40 tracks per side • 9 sectors per track • 360 sectors per side • 2 sides • 720 sectors total • 360 KBytes total capacity

  20. Double-sided, high-density (DSHD) 5¼" Floppy Disk • 80 tracks per side • 15 sectors per track • 1200 sectors per side • 2 sides • 2400 sectors total • 1200 KBytes total capacity

  21. Double-sided, double-density (DSDD) 3½" Floppy Disk • 80 tracks per side • 9 sectors per track • 720 sectors per side • 2 sides • 1440 sectors total • 720 KBytes total capacity

  22. Double-sided, high-density (DSHD) 3½" Floppy Disk • 80 tracks per side • 18 sectors per track • 1440 sectors per side • 2 sides • 2880 sectors total • 1.44 MBytes total capacity

  23. High-density, 36-Sectors (HD-36) 3½" Floppy Disk • 80 tracks per side • 36 sectors per track • 2880 sectors per side • 2 sides • 5760 sectors total • 2.88 MBytes total capacity

  24. Hard Drive vs. Floppy Drive

  25. Start with a non-magnetic platter. Floppy Disk - Mylar Hard Disk - Metal, Ceramic, or Glass 25

  26. Coat with a thin layer of magnetic material. 26

  27. The disk surface is divided into tracks. 27

  28. Track 79 Track 1 Track 0 28

  29. Side 1, Track 0 Side 2, Track 0 29

  30. Most Hard Drives Have Multiple Platters. Platter1, Track1 Platter2, Track1 Platter3, Track1 Platter4, Track1 30

  31. The eight track 1’s are referred to collectively as “Cylinder 1.” 31

  32. Read\Write Head Platter 32

  33. Read\Write Head Disk Read/Write Head

  34. 34

  35. 35

  36. One Sector = 512 Bytes 36

  37. 1 17 2 16 3 15 4 14 5 13 6 12 7 11 10 8 9

  38. 1:3 Interleave 1 12 6 7 13 17 2 11 8 5 14 16 3 10 4 9 15

  39. 1:1 Interleave 1 17 2 16 3 15 4 14 5 13 6 12 7 11 10 8 9

  40. Cluster 40

  41. Cluster • The smallest unit of disk space that OS can allocate to a file. • It consists of one or more sectors. • Generally, the larger the disk drive; the more sectors per cluster.

  42. File Allocation Table (FAT) • OS’s road map to the disk drive. • How OS keeps track of which clusters belong to which files. • How OS keeps track of bad sectors. • Two copies maintained and kept up to date by OS.

  43. Formatting • Low Level Formatting - Performed by the Disk Drive Manufacturer. • High Level Formatting - Performed by the PC User via the FORMAT Command.

  44. Low-Level Formatting Blank Disk Sectors and tracks defined 44

  45. Low Level Formatting • Performed at the factory. • Converts the single blank surface into tracks and sectors. • Finds and remaps bad spots on the disk so that the operating system can avoid them.

  46. High Level Formatting • Originally performed by the vendor of the computer. • Creates Boot Record, FAT, and the Root Directory. • Performed with the FORMAT Command.

  47. Partitioning • Makes the hard disk compatible with the operating system. • Prepares the hard disk for high-level format. • Divides the hard disk into two or more partitions or makes it all one large partition. • Performed with the FDISK command.

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