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STORAGE

STORAGE. PENGANTAR TEKNOLOGI INFORMASI (A). STMIK JAKARTA STI&K 2012. 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.

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STORAGE

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  1. STORAGE PENGANTAR TEKNOLOGI INFORMASI (A) STMIK JAKARTA STI&K 2012

  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 • Number of bytes (characters) a storage medium can hold What iscapacity?

  4. Storage Memory(most RAM)(chips on motherboard) Screen Display Storage Medium(floppy disks, Zip disks,hard disks, CDs) • Storage medium is nonvolatile—contents retained when power is off • Memory is volatile—holds data and instructions temporarily ON OFF Display appears Display disappears Volatile Data andinstructions available to user Data and instructions erased Contents available to user Contents retained Nonvolatile How does volatility compare?

  5. Storage Functions as source of input Creates output 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 What is astorage device?

  6. 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 CDs and DVDs Software, backups, movies, music Miniature Storage Media Digital pictures or small files tobe transported Tape Backups Floppy Disk Small files to be transported • Time it takes storage device to locate item on storage medium • Time required to deliver item from memory to processor fastertransferrates slowertransferrates What isaccess time?

  7. Floppy Disks 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 What is afloppy disk?

  8. Floppy Disks • Device that reads from andwrites to floppy disk Floppy disk drive built intoa desktop computer • One floppy drive, named drive A • If two floppy drives, second designated as drive B • Also called secondary storage External floppy disk drive attaches toa computer with a cable What is afloppy disk drive?

  9. Floppy Disks Step 1.When you insert the floppy disk into drive, shutter moves to the side to expose the recording surface on disk. Step 2.When you initiate a disk access, circuit board on drive that contains electronics sends signals to control movement of read/write heads until they barely touch surface (film) inside floppy disk’s shell. Step 6.Read/write heads read data from and write data on floppy disk. Step 5.Motor positions read/write heads over correct location on recording surface of disk. Step 3.For write instructions, circuit board verifies whether or not disk can be written on. Step 4.Motor spins a shaft, which causes surface inside floppy disk’s shell to spin. How does a floppy disk drive work?

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

  11. Floppy Disks Capacity: 1.44 MB Sides: 2 Tracks: 80 Sectors per track: 512 Sectors per disk: 2880 • 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 How do you compute a disk’s storage capacity?

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

  13. Hard 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 actualdiskcapacity What are characteristics of a hard disk?

  14. Hard Disks 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. How does a hard disk work?

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

  16. Hard Disks • 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 What is ahead crash?

  17. Hard Disks processor disk cache first requestfor data—to disk cache second requestfor data—to hard disk hard disk • Portion of memory that processor uses to store frequently accessed items What is adisk cache?

  18. 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 What areexternal hard disksandremovable hard disks?

  19. Hard Disks 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?

  20. Hard Disks • 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 What is anInternet hard drive?

  21. CDs and DVDs 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 CD or DVD drive, most play audio CDs Push the same buttonto close the tray. What areCDs and DVDs?

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