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MULTIMEDIA TECHNOLOGY SMM 3001

MULTIMEDIA TECHNOLOGY SMM 3001. SECONDARY STORAGE & INPUT/OUTPUT DEVICES. Secondary Storage & Input/Output Devices. Content (Text book Chapter 5) Secondary storage Storage Hierarchy SASD DASD FILE FAT INPUT Device OUTPUT Device. Secondary Memory (Storage).

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MULTIMEDIA TECHNOLOGY SMM 3001

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  1. MULTIMEDIA TECHNOLOGYSMM 3001 SECONDARY STORAGE & INPUT/OUTPUT DEVICES

  2. Secondary Storage & Input/Output Devices • Content (Text book Chapter 5) • Secondary storage • Storage Hierarchy • SASD • DASD • FILE • FAT • INPUT Device • OUTPUT Device

  3. Secondary Memory (Storage) • Backup or alternative storage in place of (volatile) RAM • Cheaper, mass storage for long term use • Secondary memory devices (and media) are distinguished by their capacities, speed, and cost

  4. Secondary Storage • Secondary Storage • Stores large amounts of data, instructions, and information more permanently than main memory • Devices for secondary storage • Magnetic tape • Magnetic disks • Compact Disk Read-Only • Memory (CD-ROM) • Write Once Read Many - (WORM) • Magneto-optical disks • Redundant Array of Independent/Inexpensive Disks (RAID)

  5. Secondary Storage • Devices for secondary storage (cont’) • Optical disks • Digital Video Disks • Memory cards • Flash memory • Removable storage

  6. Types of Memory Access • RANDOM ACCESS • items are independently addressed • access time is constant • DIRECT ACCESS • items are independently addressed in regions • access time is variable—though not significantly • SEQUENTIAL ACCESS • items are organized in sequence (linearly) • access time is significantly variable

  7. Class of Secondary Storage • SEQUENTIAL ACCESS STORAGE DEVICES AND MEDIA (SASD) • Media are constrained by the linear physical organization • Example : magnetic tape • DIRECT ACCESS STORAGE DEVICES AND MEDIA (DASD) • Media are organized to permit immediate access of data items without having to search the content of stored data. • magnetic floppy disks • magnetic hard disks • optical discs

  8. Class of Secondary Storage -(cont’) • DIRECT ACCESS STORAGE DEVICES AND MEDIA (DASD) • Media are organized to permit immediate access of data items without having to search the content of stored data. (Data retrieved without the need to read or pass other data in sequence) • magnetic floppy disks • magnetic hard disks • optical discs

  9. Memory Hierarchy I

  10. Memory Hierarchy I -(cont’) Inverse relationship between cost and speed • RAM – the fastest form of memory and the most expensive in term of the cost per bit • Next level is magnetic hard disk. These drives and their media are much more economical in their cost per bit than RAM but significantly slower. • RAM – nanosecond (billion of a second) • H/D – microsecond (million of a second)

  11. Memory Hierarchy I-(cont’) • Removable hard disk have smaller capacities than comparably sized non-removable magnetic hard disks, but their cost per bit is still more economical. • Optical disk have greater capacities than magnetic hard disks and a lower cost per bit. • Floppy disk have low capacities and inexpensive. • At the bottom of the hierarchy is magnetic tape.

  12. Memory Hierarchy II

  13. Memory Hierarchy II-(cont’) Operational perspective (off-line storage and on-line storage) • On-line storage is continually attached to and therefore constantly available to the system. Example : magnetic hard disk. • Off-line storage is the media detached and stored separately, apart from the system. Example : magnetic tape, floppy disk and removable hard-disk. Usually used for system backup.

  14. Memory Hierarchy II -(cont’) • Memory hierarchy from an operational perspective shows how data flows within the system during processing. • Information that is currently being processed must be transferred to and stored in main memory. • Data that is used often for processing or is about to be processed is usually transferred to and stored on magnetic hard disks. • Optical disks, removable hard disk and floppy disks can serve as entry points for data into a system.

  15. Magnetic particles Top coat Substrate Back coat SASD(Example : magnetic tape) Tape is usually a plastic compound having several layers.

  16. Example : magnetic tape – cont’ • Tape Is usually a plastic compound having several layers. The top is composed of a thin coat containing magnetic particles. • This layer is attached to a substrate for stability and sometimes a back coating.The thin coat in the top layer is typically based on ferrite alloy.

  17. Example : magnetic tape – cont’ • The atoms of these alloys are easily magnetized. The magnetic tape is fed through a device called a tape drive. Which can wind and unwind the tape, thereby exposing the surface to a sensing device called the read/write head. • Read/write head contains an electrical coil is charged as the tape passes over it. This establishes a uniform polarity for the portion of the surface that it contacts.

  18. Example : magnetic tape–cont’ • stores data represented by magnetized particles in linear tracks • magnetized clusters or domains are aligned to represent binary codes

  19. Example : magnetic tape–cont’

  20. Magnetic Tape Formats • LONGITUDINAL • older format used for record-keeping • SERPENTINE • used for system backups • HELICAL SCAN • high capacity formulation used for system backups and archives

  21. Magnetic Tape Formats (cont’) LONGITUDINAL TRACKING

  22. Magnetic Tape Formats (cont’) SERPENTINE TRACKING

  23. Magnetic Tape Formats (cont’) HELICAL SCAN TRACKING

  24. Magnetic Tape Formats (cont’) How data is organized on tape? xExample : ‘JOHN’ will store and 4 bit is used for 1 character J = 0110 O = 1110 H = 1010 N = 0010

  25. Track J O H N Track Longitudinal Tracking Data is organized and read parallel stored JOHN

  26. Serpentine Tracking Data is organized sequently in a single track Stored JOHN J O H N 0 1 1 0 1 1 1 0 1 0 1 0 0 0 1 0

  27. Helical Scan Tracking The tracks are arranged in a spiral that supports a greater data density per square inch compared to the other formats.

  28. Varieties of Tape • 9-track cartridge • quarter-inch cartridge (QIC) • digital linear tape (DLT) • digital audio tape (DAT) • 8mm

  29. Comparing Magnetic Tape Format • Data density – potential number of bits per square inch • Transfer rate – how fast data can be transferred from the tape to the computer once it is located on the tape. • Capacity - how much raw or uncompressed data can be stored.

  30. DASD • Magnetic hard and floppy disks • Removable hard disks • Optical discs • CD-ROM, CD-R, • WORM, • magneto-optical

  31. DASD (cont’) • All DSAD store data on circular path called tracks. Each track is divided into segments called sectors and have 2 formats : • CAV– Constant angular velocity • CLV – Constant Linear Velocity.

  32. DASD (cont’) GEOMETRY: TRACKS and SECTORS

  33. DASD Media • CAV — constant angular velocity (e.g., floppy and hard disks) • CLV — constant linear velocity (e.g., optical discs) • Zoned CAV — number of sectors depends upon zone

  34. DASD Media

  35. DASD (cont’) • To access the data : • the disk drive must find the proper track. The amount of time this takes is called the seek time. • to find the proper block, the disk controller must wait until the read/write head is aligned with the desired sector on that track. This is called the latency time.

  36. DASD (cont’) To access the data : • Once positioned over the proper sector, the sensor can read or write the data block. This is called the read/write time.

  37. Direct Access (cont’) • 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

  38. FLOPPY DISKS 5.25 and 3.5 inch diskettes 1.44 – 2.88 MBytes capacity inexpensive, archival uses for small amounts of data HARD DISKS 3.5 inch, multiple disk, sides (cylinders) high capacity Rather expensive, on-line storage Magnetic Disks

  39. Magnetic Disks (con’t) • Different between hard disks and • floppy disk • Disk rotation speed • Hard disk=3600 rpm (revolutions per minute) • Floppy disk=600 rpm • Disk organization • Hard disks usually contain fixed multiple disks • that rotate together. Thus, the sectors on each • disk are accessible at the same time to aligned • read/write heads.

  40. Magnetic Disks (con’t) • Different between hard disks and floppy disk • Data density • Hard disks have higher data density because permit a greater number tracks.

  41. New Technology of Magnetic Disc • Removable Hard Discs – High capacity offline storage. • RAID (Redundant Array of Inexpensive Disk Drives) – two or more disks and drives into a single functioning system.

  42. Optical Discs • Compact Disc–Read Only Memory (CD-ROM) • archived and published information • high capacity • Compact Disc–Recordable (CD-R) • recordable • readable using CD-ROM technology

  43. Optical Discs-(con’t) • Write Once, Read Many (WORM) • high capacity archival storage • Magneto-Optical Discs • erasable, high capacity, on-line storage alternative • Digital Versatile Discs (DVD) • Very high capacity, read-only storages

  44. Advantage & Disadvantage of Optical Media Advantage of optical media • Capability of storing greater amount of data in a more durable form (as long as the surface is not scratch) • Cheaper to update • Easier to distribute • Ability for direct access compared to magnetic tape

  45. Advantage & Disadvantage of Optical Media (cont’) Disadvantage • Access time – still less than magnetic tape • Time cycle for music/audio is slow • Overcome with the use of double, triple or quad speed CD-ROM drive

  46. CD-ROM • Based on technology of compact disc digital audio (CDDA) with 120-mm diameter disk • Capable of storing up to 650MB of data. • Using CLV format, which counts for almost 400 times the capacity of a standard floppy disk. • Data stored on is permanent or read-only memory. • Has spin rates between 200 and 500 rpm (single-speed drives)

  47. CD-ROM • Multi-speed drives was later introduced :- • Single speed (1X) 150KB • Double speed (2X) 300KB • Quadruple speed (4X) • 12X speed • 16X speed • 24X speed and even higher

  48. CD-ROM (con’t) • Lacquered plastic disc encases a thin sheet of reflective metal – usually aluminum – that covers a plastic base that has been stamped permanently with series of embossed pits of microscopic size. • The pits are depressions surrounded by reflective areas called lands.

  49. CD-ROM (con’t)

  50. CD-ROM (con’t) • Read Process • A laser beam is projected across the bottom of spinning disc • The beam is controlled by a drive mechanism that can pick out single tracks • A photo detector senses the reflective properties of the focused beam on the disc • From the bottom, pits are actually protrusions that scatter the light and the land areas reflect light straight back to the detector • Consequently, pits and lands differ in reflective intensity

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