1. Understanding Computers, 12 th Edition, Enhanced Chapter 3 1 Storage

2. Understanding Computers, 12 th Edition, Enhanced 2 Overview This chapter covers: Common characteristics of storage systems Magnetic disk storage systems Optical disc storage systems Other types of storage, such as flash memory, magnetic tape, remote storage, smart cards, Solid State Drives, and Holographic storage.

3. Understanding Computers, 12 th Edition, Enhanced 3 Properties of Storage Systems: Storage Devices and Media Involve two physical parts: a storage device and a storage medium. Can be internal (located inside the system unit), or external (located outside the system unit). Storage devices are identified by names and/or letters (e.g. C for first hard drive).

4. Understanding Computers, 12 th Edition, Enhanced 4 Properties of Storage Systems: Non-Volatility Storage media are non-volatile: When power to the device is shut off, data stored on the medium remains. This is in contrast to most types of memory, which are volatile.

5. Understanding Computers, 12 th Edition, Enhanced 5 Properties of Storage Systems: Removable vs. Fixed Media Fixed media: typically faster and less expensive. Removable media: unlimited capacity and can be easily transported and secured.

6. Understanding Computers, 12 th Edition, Enhanced 6 Properties of Storage Systems: Random vs. Sequential Access Random access ( direct access ): data can be retrieved in any order, independent of its physical location (most types of storage media). Sequential access: data can be retrieved only in the same sequence in which it is physically stored (magnetic tape).

7. Understanding Computers, 12 th Edition, Enhanced 7 Properties of Storage Systems: Logical vs. Physical Representation Logical file representation refers to the users view of the way data is stored (filename, folders, etc.). Physical file representation is the actual physical way the data is stored on the storage media as viewed by the computer.

8. Understanding Computers, 12 th Edition, Enhanced 8 Magnetic Disk Systems Magnetic disks are the most widely used storage medium in computers today. Data is stored by magnetizing particles on the storage medium. Two common types: Floppy disks Hard disks

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10. 10 Floppy Disks and Drives Floppy disk characteristics Typically 3½ inches in diameter. Typically hold 1.44 megabytes. Inserted into floppy disk drive to be read from or written to.

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12. Understanding Computers, 12 th Edition, Enhanced 12 Floppy Disk Geometry Disk is divided into tracks, sectors, and clusters. The disks file directory keeps track of the contents of the disk so files can be retrieved (by filename) at a later time.

13. Understanding Computers, 12 th Edition, Enhanced 13 Floppy Disks and Drives, Contd. Using floppy disks Must be inserted into the proper drive in the proper direction. Should not be removed when the disk is being accessed. High-capacity removable magnetic disks and drives Zip disks (750 MB) SuperDisks (240 MB)

14. Understanding Computers, 12 th Edition, Enhanced 14 Hard Disk Drives Hard drive characteristics Metal disk onto which data is stored magnetically. Disks are usually permanently sealed inside the hard driveallows faster speeds and storage of more data than removable systems. Can be internal or external.

16. Understanding Computers, 12 th Edition, Enhanced 16 Hard Disk Drives, Contd. Hard drive characteristics, contd Organized into tracks, sections, clusters, and cylinders (the collection of tracks located in the same location on a set of hard disk surfaces). Read/write head doesnt touch the surface of the disk. Bumping PC when disk is being accessed or dust or other obstacles on a hard-disk system can cause a head crash and damage the surface of the disk.

17. Understanding Computers, 12 th Edition, Enhanced 17 Hard Disk Drives, Contd. Disk access time. Factors: seek time, rotational delay, data movement time Can use multiple partitions. Disk cachestrategy for speeding up system performance. Hard drive standards (EIDE, SCSI, Fibre Channel, USB).

18. Understanding Computers, 12 th Edition, Enhanced 18 Hard Disk Drives, Contd. Portable hard drive systems Offer large storage capacities and portability. Either entire drive or just hard disk cartridge is transported.

19. Understanding Computers, 12 th Edition, Enhanced 19 Hard Disk Drives, Contd. Storage systems for large computer systems and networks Storage servers containing racks of hard drives. Network attached storage (NAS). Storage area networks (SANs). RAID (for increased performance and/or fault tolerance).

20. Understanding Computers, 12 th Edition, Enhanced 20 Optical Disc Systems Laser beams write and read data packed at very tight storage densities, many times finer than that of a typical magnetic disk. Are typically 4½-inch discs, but can be a variety of shapes and sizes. Data is stored optically on a continuous spiral track. Can be CDs or DVDs.

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22. Understanding Computers, 12 th Edition, Enhanced 22 Read-Only Discs: CD-ROM and DVD- ROM Discs CD-ROM discs cannot be written to or erased and typically hold 650 MB (e.g. music CDs). DVD-ROM discs are similar to CD-ROM discs, but have higher capacity of 4.7 GB to 17 GB (e.g. movie DVDs). Data is stored by burning pits into the disc surface that can be read using a laser beam.

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24. Understanding Computers, 12 th Edition, Enhanced 24 Recordable Discs: CD-R, DVD-R, and DVD+R Discs Recordable discs can be written to, but not erased or rewritten. Burning a CD or DVD permanently records data onto the disc. CD-R discs are commonly used to store data and for custom music CDs. DVD-R/DVD+R discs are commonly used for home movies and other high-capacity applications.

25. Understanding Computers, 12 th Edition, Enhanced 25 Rewritable Discs: CD-RW, DVD-RW, DVD+RW, DVD-RAM, BD-Rom and HD- DVD-ROM Discs Rewritable discs can be used in the same way as magnetic disksdata can be stored and erased as needed. Phase-change technology is used to record data onto the disc using reflectivity. Rewritable discs can be erased by reverting the reflectivity back to the original state. Blue laser discs are an emerging higher-capacity (25 GB) form of optical disc.

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27. Understanding Computers, 12 th Edition, Enhanced 27 Other Types of Storage Systems Magneto-optical discs A combination of magnetic and optical technology. Can store up to 9.1 GB per disk.

28. Understanding Computers, 12 th Edition, Enhanced 28 Other Types of Storage Systems, Contd Flash memory media Chip-based storage. Solid state storage systemhas no moving parts, so are more shock-proof and portable than conventional storage systems. Commonly used with digital cameras, digital music players, handheld PCs, notebook computers, smart phones, etc.

29. Understanding Computers, 12 th Edition, Enhanced 29 Other Types of Storage Systems, Contd Flash memory media, contd. Common forms of flash memory: Flash memory sticks. Flash memory cardsCompactFlash, Secure Digital (SD), MiniSD, MultiMedia (MMC), SmartMedia, and xD Picture cards. Flash memory drives, such as USB flash drives.

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31. Understanding Computers, 12 th Edition, Enhanced 31 Other Types of Storages Systems, Contd Magnetic tape systemsplastic tape that is magnetized to represent data. Used primarily for backup and archival purposes (sequential access only). Read from and written to via a tape drive. Most tape media are in the form of cartridge tapes, though detachable-reel tapes exist as well.

32. Understanding Computers, 12 th Edition, Enhanced 32 Holographic Storage Systems Storing data in 3-D same shape as DVD, but it stores 18-64 times as much data. stores bytes throughout its depth, not just on one flat or two layers. A blue laser beam burns layers at several angles Drive and 300-gigabyte disks, available in 2009 form InPhase.InPhase

33. Holographic storage system: 462 CDs 64 DVDs 12 BDs Target market is HD movie archives, data centers etc. and no consumer version. Drive (also called Tapestry) is about $18,000 (about EGP 99,000) disk is about $180 (about EGP990) Source: http://www.inphase-technologies.com/products/markets.asp?subn=3_3 Holographic Storage Systems, contd

34. Understanding Computers, 12 th Edition, Enhanced 34 Other Types of Storage Systems, Contd Remote storage storage devices that are not directly connected to your PC. Network storage accessible through a local network. Online storage accessible via the Internet and used for back up, as well as to transfer files to others.

35. Understanding Computers, 12 th Edition, Enhanced 35 Other Types of Storage Systems, Contd Smart card: credit-card-sized piece of plastic that contains some type of computer circuitry. Holds less than a few megabytes. Commonly used to store prepaid amounts of digital cash or personal information. Smart card readers are attached to a PC or built into a cell phone, keyboard, or other device.

37. Understanding Computers, 12 th Edition, Enhanced 37 Comparing Storage Alternatives Factors to consider: speed, expense, portability, storage capacity, and compatibility. Most PC users require: Hard drive CD or DVD drive Floppy drive Additional devices (flash memory card reader, etc.) as needed for the devices being used in conjunction with the PC (e.g. digital camera)