lecture7 Input Output and Secondary Memory 2013

Hard disk drive magnetic disks floppy disks 525 and 35

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Unformatted text preview: loppy / Hard Disks Floppy DiskῊfits in your shirt pocket ! Hard Disk Drive Magnetic Disks • FLOPPY DISKS • 5.25 and 3.5 inch diskettes • 1.44 – 2.88 MBytes capacity • access: drive speeds – 600 r.p.m. • inexpensive, archival uses for small amounts of data • HARD DISKS • 3.5 inch has approx 3,000 tracks per side • multiple disk, sides (cylinders) • high capacity 1 Terabyte • access: drive speeds – 3,600 up to 7,200 r.p.m. • on-line storage Direct Access Storage Devices • magnetic hard and floppy disks • removable hard disks • optical discs • CD-ROM, CD-R, DVD • DVD-R GEOMETRY: GEOMETRY: TRACKS and SECTORS TRACKS Direct Access • SEEK — controller advances read/write head to proper track • LATENCY — waits for proper sector to rotate under head • READ/WRITE — disk head scans the sector for read or write Disk vs. File Organization • data is stored in blocks • blocks occupy sectors • sectors on tracks • files have names • files are indefinite in size • files may be updated (in part or whole) Files may become fragmented over time, which causes data transfers to slow Optical Discs • Compact Disc–Read Only Memory (CD-ROM) • archived and published information • Relatively high capacity (650 Mbytes) • Compact Disc–Recordable (CD-RW • recordable • readable using CD-ROM technology • Digital Versatile Discs (DVD)/DVD-R) • Very high capacity, read-only storages (5-15 Gbytes) • Multiple Layers, tighter spacing in the same size as CD • Now BLUE RAY and DVD-HD! (3-10 times the capacity of today’s DVDs) Optical Drives Reading and Writing • discs are “burnt” one at a time • high intensity laser beam used for reading/recording pregrooved tracks • low intensity beam for reading/ higher intensity for burning Flash Me...
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This document was uploaded on 03/11/2014 for the course CSCI 0020 at Brown.

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