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Lecture 9 Storage

Lecture 9 Storage. www.shahidrasul.com. Storage. What is storage ?. Holds data, instructions, and information for future use. Storage medium is physical material used for storage. Also called secondary storage. Storage. Kilobyte (KB). 1 thousand. Megabyte (MB). 1 million. Gigabyte (GB).

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Lecture 9 Storage

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  1. Lecture 9Storage www.shahidrasul.com

  2. Storage • What isstorage? • Holds data, instructions, and information for future use • Storage mediumis physical material used for storage • Also called secondary storage

  3. Storage Kilobyte (KB) 1 thousand Megabyte (MB) 1 million Gigabyte (GB) 1 billion Terabyte (TB) 1 trillion Petabyte (PB) 1 quadrillion Exabyte (EB) 1 quintillion Zettabyte (ZB) 1 sextillion Yottabyte (YB) 1 septillion • What iscapacity? • Number of bytes (characters) a storage medium can hold

  4. Storage Functions as source of input Creates output • What is astorage device? Hardware that records and retrieves items to and from storage media Reading Process of transferring items from storage media to memory Writing Process of transferring items from memory to storage media

  5. Storage Stores … Primary Storage Memory (most RAM) Items waiting to be interpretedand executed by the processor Secondary Storage Hard Disk Operating system, applicationsoftware, user data and information Flash Memory Cards and USB Flash Drives Digital pictures or files to be transported CDs and DVDs Software, backups, movies, music Tape Backups Floppy Disk Small files to be transported • What isaccess time? • Time it takes storage device to locate item on storage medium • Time required to deliver item from memory to processor fastertransferrates slowertransferrates

  6. Magnetic Disks Trackis narrow recording bandthat forms fullcircle on disk Sectorstores up to512 bytesof data • What aretracks andsectors? Formatting prepares disk for use and marks bad sectors as unusable

  7. Magnetic Disks • What is afloppy disk? shutter • Portable, inexpensive storage medium (also called diskette) shell liner magneticcoating Thin, circular, flexible film enclosedin 3.5” wide plastic shell metal hub flexible thin film www.shahidrasul.com

  8. Magnetic Disks Capacity: 1.44 MB Sides: 2 Tracks: 80 Sectors per track: 18 Bytes per sector: 512 Sectors per disk: 2880 • How do you compute a disk’s storage capacity? • Multiply number of sides, number of tracks, number of sectors per track, and number of bytes per sector • For high-density disk: 2 sides  80 tracks  18 sectors per track  512 bytes per sector = 1,474,560 bytes Characteristics of a3.5-inch High-DensityFloppy Disk www.shahidrasul.com

  9. Magnetic Disks hard disk installedin system unit • What is ahard disk? • High-capacity storage • Consists of several inflexible, circular platters that store items electronically • Components enclosed in airtight, sealed case for protection www.shahidrasul.com

  10. Magnetic Disks Sample Hard Disk Characteristics Advertised capacity 120 GB Platters 3 Read/write heads 6 Cylinders 16,383 Bytes per second 512 Sectors per track 63 Sectors per drive 234,441,648 Revolutions per minute 7,200 Transfer rate 133 MB per second Access time 8.9 ms • What are characteristics of a hard disk? actualdiskcapacity

  11. Magnetic Disks • How does a hard disk work? Step 3.When software requests a disk access, read/write heads determine current or new location of data. Step 2.Small motor spins platters while computer is running. Step 4.Head actuator positions read/write head arms over correct location on platters to read or write data. Step 1.Circuit board controls movement of head actuator and a small motor. www.shahidrasul.com

  12. Magnetic Disks platter • What is acylinder? track • Vertical section of track through all platters sector • Single movement of read/write head arms accesses all plattersin cylinder read/writehead platter sides cylinder

  13. Magnetic Disks • What is ahead crash? • Occurs when read/write head touches platter surface • Spinning creates cushion of air that floats read/write head above platter • Clearance between head and platter is approximately two-millionths of an inch • A smoke particle, dust particle, or human hair could render drive unusable hair read/write head dust clearance smoke platter www.shahidrasul.com

  14. Magnetic Disks processor disk cache first requestfor data—to disk cache second requestfor data—to hard disk hard disk • What is adisk cache? • Portion of memory that processor uses to store frequently accessed items www.shahidrasul.com

  15. Magnetic Disks • What is aminiature hard disk? • Provide users with greater storage capacities than flash memory • Some have a form factor of less than 1 inch • Storage capacities range from 2 GB to 100 GB

  16. Magnetic Disks • What areexternal hard disksandremovable hard disks? • Used to back up or transfer files Removable hard disk—hard diskthat you insert and removefrom hard disk drive External hard disk—freestandinghard disk that connects to system unit www.shahidrasul.com

  17. Magnetic Disks SATA (Serial Advanced Technology Attachment) controller uses serial signals to transfer data, instructions, and information EIDE (EnhancedIntegratedDrive Electronics) controller supports four hard disks, provides connections for CD and DVD drives Chip and circuits that control transfer of items from disk SCSI(SmallComputerSystemInterface)controller supports up to fifteendevices including hard disks, CDand DVD drives, tape drives, printers,scanners, network cards • What is adisk controller?

  18. Magnetic Disks • What is online storage? • Service on Web that provides storage for minimal monthly fee • Files can be accessed from any computer with Web access • Large files can be downloaded instantaneously • Others can be authorized to access your data www.shahidrasul.com

  19. Optical Discs Next • What areoptical discs? Push the button toslide out the tray. • Flat, round, portable metal discs made of metal, plastic, and lacquer • Can be read only or read/write Insert the disc,label side up. • Most PCs include an optical disc drive Push the same buttonto close the tray. p. 366 Fig. 7-19

  20. Optical Discs disc label lens lens pit land Step 3.Reflected light is deflected to alight-sensing diode, which sends digital signals of 1 to computer. Absence of reflected light is read as digital signal of 0. 0 1 prism prism light-sensingdiode light-sensingdiode laserdiode laserdiode • How does a laser read data on an optical disc? Step 2.If light strikesa pit, it scatters. If light strikes a land, it is reflected back toward diode. Step 1.Laser diode shines a light beam towarddisc.

  21. Optical Discs • How is data stored on an optical disc? • Typically stored in singletrack • Track divided into evenly sizedsectorsthat store items single trackspirals to edgeof disc disc sectors

  22. Optical Discs • How should you care for an optical disc? Do not exposethe disc to excessiveheat or sunlight Do store thedisc in a jewelbox whennot in use Do noteat, smoke, ordrink neara disc Do not stack discs Do hold a discby its edges Do not touchthe undersideof the disc

  23. Optical Discs • What is aCD-ROM? • Compactdiscread-onlymemory • Cannot erase or modify contents • Typically holds 650 MB to 1 GB • Commonly used to distribute multimedia and complex software

  24. Optical Discs • What is the data transfer rate of a CD-ROM drive? Ranges from 48X to 75X or faster 75X 75  150 KBps = 11,250 KBps or 12.25 MBps 75X is 150 KBps (KB per second) 48X: 48  150 KBps = 7,200 KBps or 7.2 MBps www.shahidrasul.com

  25. Optical Discs Stores digital versions of roll of film Film developers offer Picture CD service Can be modified using photo editing software • What is aPicture CD? Step 1.Drop off film to be developed. Mark the Picture CD box on the film-processing envelope. Step 3.At home, print images from Picture CD on your ink-jet photo printer. Step 2.When you pick up prints and negatives, a Picture CD contains digital images of each photograph. At a store, print images to Picture CD at kiosk.

  26. Optical Discs • What areCD-Rs and CD-RWs? Must haveCD recorderor CD-R drive CD-R (compact disc-recordable) —cdisc you can write on once Cannot erasedisc’s contents CD-RW (compact disc-rewritable) —ceerasable disc you can write onmultiple times Must haveCD-RW softwareandCD-RW drive

  27. Optical Discs • What is aDVD-ROM(digital versatile disc-ROM or digital video disc-ROM)? • High capacity disc capable of storing 4.7 GB to 17 GB • Must haveDVD-ROM driveor DVD player to read DVD-ROM • Stores databases, music, complex software, and movies www.shahidrasul.com

  28. Optical Discs • How does a DVD-ROM store data? • Two layers of pits are used, lower layer is semitransparent so laser can read through • Some are double-sided • Blu-Ray discs currently have a storage capacity of up to 27 GB

  29. Tape • What istape? • Magnetically coated plastic ribboncapable of storing large amountsof data at low cost • Primarily used for backup www.shahidrasul.com

  30. Tape • How is data stored on a tape? • Sequential access • Reads and writes data consecutively, like music tape • Unlike direct access — used on floppy disks, Zip disks, hard disks, CDs, and DVDs — which can locate particular item immediately www.shahidrasul.com

  31. PC Cards • What is aPC Card? • Adds capabilities to computer • Credit-card-sized device commonlyused in notebook computers

  32. Miniature Mobile Storage Media • What isminiature mobile storage media? • Storage for small mobile devices

  33. Miniature Mobile Storage Media CompactFlash Smart Media Secure Digital xD Picture Card Memory Stick • What are common types of flash memory cards? www.shahidrasul.com

  34. Miniature Mobile Storage Media • How does one type of flash memory card work?

  35. Miniature Mobile Storage Media • What is aUSB Flash Drive? • Plugs in a USB port on a computer or mobile device • Storage capacities up to 4 GB • May eventually make the floppy disk obsolete

  36. Miniature Mobile Storage Media • What is asmart card? • Stores data on microprocessor embedded in small card • Input, process, output, and storage capabilities

  37. Microfilm and Microfiche Microfilm — 100- to215-foot roll of film Microfiche — small sheet of film, usually 4”  6” • What aremicrofilmandmicrofiche? Store microscopic images of documents on roll or sheet of film Images recorded using computer output microfilm recorder

  38. Microfilm and Microfiche • How do life expectancies of various media compare? • Microfilm and microfiche have longest life of any storage media

  39. Putting It All Together Home • What are recommended storage devices for home users? • 80 GB hard disk • Online storage • CD or DVD drive • Card reader/writer • USB flash drive and/or 3.5-inch floppy disk drive www.shahidrasul.com

  40. Putting It All Together Small Office/Home Office (SOHO) • What are recommended storage devices for small office/home office (SOHO) users? • 750 MB Zip drive • 120 GB hard disk • Online storage • CD or DVD drive • External hard drive for backup • USB flash drive and/or 3.5-inch floppy disk drive www.shahidrasul.com

  41. Putting It All Together Mobile • What are recommended storage devices for mobile users? • 80 GB hard disk • Online storage • CD or DVD drive • Card reader/writer • Portable hard disk for backup • USB flash drive, and/or 2 GB PC Card hard disk, and/or 3.5-inch floppy disk drive www.shahidrasul.com

  42. Putting It All Together Power • What are recommended storage devices for power users? • CD or DVD drive • 300 GB hard disk • Online storage • Portable hard disk for backup • USB flash drive and/or 3.5-inch floppy disk drive www.shahidrasul.com

  43. Putting It All Together Large Business • What are recommended storage devices for large business users? • Desktop computer • 160 GB hard disk • CD or DVD drive • Smart card reader • Tape drive • USB flash drive and/or 3.5-inch floppy disk drive • Server or Mainframe • Network storage server • 40 TB hard disk system • CD-ROM or DVD-ROM server • Microfilm or microfiche www.shahidrasul.com

  44. Summary of Storage Floppy disks Recordable DVDs Zip disks Rewritable DVDs Internal hard disks Tape Portable hard disks PC Cards Recordable CDs Flash memory cards and USB flash drives Rewritable CDs Smart cards, microfilm, and microfiche DVD-ROMs Lecture Complete

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