Faizan Chap 07 Storage

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Faizan Chap 07 Storage

  1. 1. STORAGE CHAPTER 7 by Faizan Tariq
  2. 2. kilobyte (KB) 1 thousand Megabyte (MB) 1 million Gigabyte (GB) 1 billion Terabyte (TB) 1 trillion Petabyte (PB) 1 quadrillion STORAGE <ul><li>What is Storage? </li></ul><ul><li>holds data, instructions, and information for future use </li></ul><ul><li>storage medium is physical material used for storage </li></ul><ul><li>What is Capacity? </li></ul><ul><li>number of bytes (characters) a storage medium can hold </li></ul>
  3. 3. What is a storage device? <ul><li>Hardware that records and retrieves items from storage media </li></ul><ul><li>Reading : Process of transferring items from storage media to memory </li></ul><ul><li>Functions as source of input </li></ul><ul><li>Writing : Process of transferring items from memory to storage media </li></ul><ul><li>creates output </li></ul>STORAGE
  4. 4. STORAGE <ul><li>What are tracks and sectors? </li></ul><ul><li>Tracks is narrow recording band that forms full circle disk </li></ul><ul><li>Sectors stores up to 512 bytes of data </li></ul><ul><li>What is a floppy disk ? </li></ul><ul><li>Portable , inexpensive storage medium (also called as diskette) </li></ul>
  5. 5. Magnetic disks <ul><li>What is a floppy disk drive ? </li></ul><ul><li>Device that reads from and writes to floppy disk </li></ul><ul><li>Also called secondary storage </li></ul><ul><ul><li>Floppy disk drive built into a desktop computer </li></ul></ul><ul><ul><li>External floppy disk drive attaches a computer with a cable </li></ul></ul>
  6. 6. Magnetic disks <ul><li>How do you compute a disk's storage capacity? </li></ul><ul><li>Multiply number of sides, number of tracks, number of sectors per track, and number of bytes per sector </li></ul><ul><li>For high density disk 2 sides x 80 tracks x 18 sectors per track x 512 bytes per sector = 1,474,560 bytes </li></ul><ul><li>Characteristics of a 3.5 inch High density Floppy disk </li></ul>Capacity: 1.44 MB Slides: 2 Tracks: 80 Sector per track: 18 Bytes per second: 512 Sector per disk: 2880
  7. 7. Magnetic disks <ul><li>What is a Zip disk ? </li></ul><ul><li>Magnetic medium that stores 100 MB to 750 MB of data </li></ul><ul><li>Used to back up and to transfer files </li></ul><ul><li>: backup is duplicate of files, program, or disk in </li></ul><ul><li>case of original is lost. </li></ul><ul><li>Zip disk requires a Zip drive high capacity drive that reads </li></ul><ul><li>and writes on a Zip disk </li></ul><ul><li>What is a hard disk ? </li></ul><ul><li>High capacity storage </li></ul><ul><li>Consist of several inflexible, circular platters that stores items electronically </li></ul><ul><li>Components enclosed in alright, sealed case for protection </li></ul>
  8. 8. Advertised capacity 120GB Platters 3 Read/write heads 6 Cylinders 16,383 Bytes per seconds 512 Sectors per track 63 Sectors per drive 234,441,648 Revolution per minute 7,200 Transfer rate 133MB per second Access time 8.9 ms Magnetic disks <ul><li>What are characteristics of a hard disk? </li></ul><ul><li>Simple hard drive characteristics </li></ul><ul><li>What is a cylinder ? </li></ul><ul><li>Vertical section of track through all platters , single movement of read/write head </li></ul><ul><li>arms access all platters in cylinder </li></ul>
  9. 9. Magnetic disks <ul><li>How does a hard disk work ? </li></ul><ul><li>Step 1 : circuit board controls movement of head actuator and a small motor. </li></ul><ul><li>Step 2 : small motor spins platter while computer is running. </li></ul><ul><li>Step 3 : when software request a disk access, read/write heads determine current or new location of data. </li></ul><ul><li>Step 4 : head actuator positions read/write arms over correct location on platters to read or write data. </li></ul><ul><li>What is a head crash ? </li></ul><ul><li>Occurs when read/write head touches platter surface </li></ul><ul><li>Spinning creates cushion of air that floats read/write above platter </li></ul><ul><ul><li>Clearance between head and platter is approximately two- millionths of an inch </li></ul></ul><ul><ul><li>A smoke particle, dust particle, or human hair could render drive unusable </li></ul></ul>
  10. 10. Magnetic disks <ul><li>What is a miniature hard disk ? </li></ul><ul><li>Provide users with greater storage capacities than flash memory </li></ul><ul><li>Some have a form factor of less than 1 inch </li></ul><ul><li>Storage capacities range from 2 GB to 100 GB </li></ul><ul><li>What is online storage ? </li></ul><ul><li>Service on web that provides storage for minimum monthly fee </li></ul><ul><li>Files can be accessed from any computer with web access </li></ul><ul><li>Large file can be downloaded instantly </li></ul><ul><li>Others can be authorized to access your data </li></ul>
  11. 11. Magnetic disks <ul><li>What are external hard disk and removable hard disk ? </li></ul><ul><ul><li>Used to back up or transfer files </li></ul></ul><ul><li>External hard disk : freestanding hard disk that connects to system unit </li></ul><ul><li>Removable hard disk : hard disk that you insert and remove from hard drive </li></ul><ul><li>What are optical discs ? </li></ul><ul><li>Flat, round, portable metal discs made of metal, plastic, and lacquer </li></ul><ul><li>Can be read only or read/write </li></ul><ul><li>Most PCs include an optical disc drive </li></ul><ul><li>What is a CD-ROM ? </li></ul><ul><li>Compact disc read- only memory </li></ul><ul><li>Cannot erase or modify contents </li></ul><ul><li>Typically holds 650 MB to 1 GB </li></ul><ul><li>Commonly used to distribute multimedia and complex software </li></ul>
  12. 12. Optical disks <ul><li>What is a DVD-ROM (digital versatile disc-ROM or digital video disc-ROM)? </li></ul><ul><li>Highly capacity disc capable of storing 4.7 GB to 17 GB </li></ul><ul><li>Must have DVD –ROM drive or DVD player to read DVD -ROM </li></ul><ul><li>Stores databases, music, complex software, and movies </li></ul><ul><li>How does a laser read data on an optical disc ? </li></ul><ul><li>Step 1 . laser diode shines a light beam toward disc </li></ul><ul><li>Step 2 . if light strikes a it scatters, if a light strikes a land, it strike a land , it is reflected back towards diode. </li></ul><ul><li>Step 3 . reflected light is deflected to a light-sensing diode, which send digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0. </li></ul>
  13. 13. Optical disks <ul><li>How should you take care of an optical disc ? </li></ul><ul><li>Do not expose the disc to excessive heat or sunlight </li></ul><ul><li>Do not smoke ,eat or drink near a disc </li></ul><ul><li>Do not stack disc </li></ul><ul><li>Do not touch the underside of the disc </li></ul><ul><li>Do store the disc in a jewel box when not in use </li></ul><ul><li>Do hold the disc by its edges </li></ul><ul><li>What are CD-Rs and CD- RWs? </li></ul><ul><li>CD-R (compact disc – recordable) disc you can write once </li></ul><ul><li>Must have CD recorder or CD-R drive </li></ul><ul><li>Cannot erase discs contents </li></ul><ul><li>CD-RW (compact disc- rewriteable) erasable disc you can write on multiple times </li></ul><ul><li>Must have CD-RW software and CD-RW drive </li></ul>
  14. 14. Tape <ul><li>What is tape? </li></ul><ul><li>Magnetically coated plastic ribbon capable of storing large amounts of data at low cost </li></ul><ul><li>Primarily used for backup </li></ul><ul><li>How is data stored on a tape ? </li></ul><ul><li>Sequential access </li></ul><ul><li>Reads and write data consecutively like a music tape </li></ul><ul><li>Unlike direct access – used on floppy, zip disks , hard disks, CDs and DVDs – which can locate particular item immediately </li></ul>

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