1 / 18

Chapter 3

Chapter 3. Storage Principles. Storage. Magnetic Floppy disks ,Hard disk ,Zip drive Optic CD-ROM, DVD Magneto optic High end drives Data on any drive are digitized; they are expressed as myriads of 0s and 1s. Interface.

emera
Download Presentation

Chapter 3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 3 Storage Principles

  2. Storage • Magnetic • Floppy disks ,Hard disk ,Zip drive • Optic • CD-ROM, DVD • Magneto optic • High end drives • Data on any drive are digitized; they are expressed as myriads of 0s and 1s.

  3. Interface • Individual drives are connected to other PC components through an Interface. • EIDE or eSATAHard disks • CD-ROM • SCSI • Hard disks (all sizes) and CD-ROM • ISA (internal) • Floppy drives ,CDROM, others connected through parallel port

  4. Floppy Disk • a data storage medium • made of a disk of thin, flexible magnetic storage medium encased in a square plastic shell. • read and write • Invented by IBM, floppy disks in 8", 5.25" and 3.5" formats

  5. Floppy Controller • governed by a controller. The controller has to be programmed at each start up. • reads data from the diskette media in serial mode (one bit at a time) • data are delivered in parallel mode (16 bits at a time) to RAM via a DMA channel.

  6. Floppy Drive • Read/Write Heads • Drive Motor • Stepper Motor • Mechanical Frame • Circuit Board

  7. Hard Disk • is a non-volatile storage device which stores digitally encoded data • is a 3.5” diameter rigid-disk drive. • consist of thin platters with a magnetic coating. • Write mode:- • If a current is applied to the coil, the head will become magnetic. • Read mode:- • If the head moves along the track without current applied to the coil, it will sense the micro magnets.

  8. Hard Disk

  9. Domains • The bits that store in microscopic magnets (called domains) on the disk. • Before recording data, the drive uses the read/write heads to orient the domains in a small region so that the magnetic poles all point in the same direction. • Then, a reversal of polarity is interpreted as a digit one. Unchanged polarity is interpreted as a digit zero.

  10. Hard Disk Speeds • disk access time • is the time required for a computer to process data from a storage device. • Access Time = Seek Time + Latency time + Data Transfer time • Seek time • is the time for the access arm to reach the desired disk track. • Latency time • the time for the rotation of the disk to bring the required disk sector under the read-write mechanism. • Data Transfer Rate • time during which data is actually read or written to medium, with a certain throughput.

  11. Other Disks

  12. Optical Storage • CD-ROM and DVD are optic readable media. • read with a very thin and precisely aimed laser beam. • the disks are removable. • the CD-ROM is an optic media. • data storage consists of millions of indentations burnt into the lacquer coated, light reflecting silver surface.

  13. Tracks • data consist of bits • bits are arranged in a pattern along the track. • has only one track, a spiral winding its way from the center to the outer edge • 5km long spiral track holds up to 650Mb data in about 5.5 billions dot (each is one bit). CD-ROM

  14. Types of Optical Media

  15. Optical media • Data can be packed much more densely in optic media than in magnetic media. • They have much longer life span. • There are different types of optical disk: • Compact Disk • CD-ROM • DVD

  16. Compact Disk • was introduced by Philips and Sony in 1980. • a small plastic disk with a reflecting metal coating. • is organized in tracks.

  17. CD-ROM • The CD-ROM (Read Only Memory) came in 1984. • are the same as the CD; the difference is in the data storage organization. • In a CD-ROM, the data are stored in sectors. The CD-ROM can hold 700 MB of data, and it is very inexpensive to produce.

  18. DVD • is a high-capacity optic media and was developed in the mid 1990s. DVD stands for Digital Versatile Disk. • The DVD is the same size as a CD but the tracks are narrower • are read by a laser beam of shorter wave-length than used by the CD-ROM drives. This allows for smaller indentations and increased storage capacity. • A single layer DVD-5 disk holds 4.7 GB. A dual-layered DVD-9 disk holds 8.5 GB. The dual-sided DVDs are named DVD-10 (9.4 GB) and DVD-18 (17 GB).

More Related