Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill Technology Education Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.

McGraw-Hill Technology Education Chapter 6A Types of Storage Devices

6A-3 Describing Storage Devices Store data when computer is off Two processes –Writing data –Reading data

6A-4 Describing Storage Devices Storage terms –Media is the material storing data –Storage devices manage the media –Magnetic devices use a magnet –Optical devices use lasers –Solid-state devices have physical switches

6A-5 Magnetic Storage Devices Most common form of storage Hard drives, floppy drives, tape All magnetic drives work the same

6A-6 Magnetic Storage Devices Floppy Disk Hard Disk Tape

6A-7 Magnetic Storage Devices Data storage and retrieval –Media is covered with iron oxide –Read/write head is a magnet –Magnet writes charges on the media Positive charge is a 1 Negative charge is a 0 –Magnet reads charges –Drive converts charges into binary

6A-8 Data Retrieval

6A-9 Magnetic Storage Devices Data organization –Disks must be formatted before use –Format draws tracks on the disk –Tracks is divided into sectors Amount of data a drive can read

6A-10 Tracks and Sectors

6A-11 Magnetic Storage Devices Finding data on disk –Each track and sector is labeled Some are reserved –Listing of where files are stored File Allocation Table (FAT) FAT32 NTFS –Data is organized in clusters Size of data the OS handles

6A-12 Magnetic Storage Devices Diskettes –Also known as floppy disks –Read with a disk drive –Mylar disk –Spin at 300 RPM –Takes.2 second to find data –3 ½ floppy disk holds 1.44 MB

6A-13 Magnetic Storage Devices Hard disks –Primary storage device in a computer –2 or more aluminum platters –Each platter has 2 sides –Spin between 5,400 to 15,000 RPM –Data found in 9.5 ms or less –Drive capacity greater than 40 GB

6A-14 Illustrated Hard Disk

6A-15 Magnetic Storage Devices Removable high capacity disks –Speed of hard disk –Portability of floppy disk –Several variants have emerged –High capacity floppy disk Stores up to 750 MB of data –Hot swappable hard disks Provide GB of data Connect via USB

6A-16 Magnetic Storage Devices Tape drives –Best used for Infrequently accessed data Back-up solutions –Slow sequential access –Capacity exceeds 200 GB

6A-17 Optical Storage Devices CD-ROM –Most software ships on a CD –Read using a laser Lands, binary 1, reflect data Pits scatter data –Written from the inside out –CD speed is based on the original Original CD read 150 Kbps A 10 X will read 1,500 Kbps –Standard CD holds 650 MB

6A-18 Optical Storage Devices DVD-ROM –Digital Video Disk –Use both sides of the disk –Capacities can reach 18 GB –DVD players can read CDs

6A-19 Recordable Optical Technologies CD Recordable (CD-R) –Create a data or audio CD –Data cannot be changed –Can continue adding until full

6A-20 Recordable Optical Technologies CD Regrettable (CD-RW) –Create a reusable CD –Cannot be read in all CD players –Can reuse about 100 times

6A-21 Recordable Optical Technologies Photo CD –Developed by Kodak –Provides for photo storage –Photos added to CD until full –Original pictures cannot be changed

6A-22 Recordable Optical Technologies DVD Recordable –Several different formats exist –None are standardized –Allows home users to create DVDs –Cannot be read in all players

6A-23 Recordable Optical Technologies DVD-RAM –Allow reusing of DVD media –Not standardized –Cannot be read in all players

6A-24 Solid State Devices Data is stored physically No magnets or laser Very fast

6A-25 Solid State Devices Flash memory –Found in cameras and USB drives –Combination of RAM and ROM –Long term updateable storage

6A-26 Solid State Devices Smart cards –Credit cards with a chip –Chip stores data –Eventually may be used for cash –Hotels use for electronic keys

6A-27 Solid State Devices Solid-state disks –Large amount of SDRAM –Extremely fast –Volatile storage –Require battery backups –Most have hard disks copying data

Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill Technology Education Chapter 6B Measuring and Improving Drive Performance

6B-29 Drive Performance Average access time –Also known as seek time –Time to find wanted data –Measured in milliseconds –Depends on two factors RPM Revolutions per minute Time to access a track –Hard drive between 6 and 12 ms –CD between 80 and 800 ms

6B-30 Drive Performance Data transfer rate –How fast data can be read –Measured in Bps or bps bits per second –Hard drive ranges from 15 to 160 MBps –CD ROMS depend on X factor 24x CD transfers 24 x 150 KBps –Floppy disks transfer at 45 KBps

6B-31 Data Transfer Rate

6B-32 Optimizing Performance Disk optimization –Handled (process) by operating system tool –Routine disk maintenance –Optimization should be run monthly

6B-33 Optimizing Performance Clean up unnecessary files –Delete temp files –Uninstall unused programs –Delete old data files –Files should be cleaned weekly

6B-34 Optimizing Performance Scan a disk for errors –Bad spots on the media –Find and correct the error Move data to a good spot Mark the spot as bad –Disks should be scanned monthly

6B-35 Optimizing Performance Defragment partition a disk –Files fragment when resaved –Fragmented files load slower –Defragment some the fragments together –Disks should be defragged monthly

6B-36 Defragment

6B-37 Optimizing Performance File compression –Shrinks the size of a file –Takes up less space on disk –Reduce a disks performance –Will increase disk capacity –PKZip, WinZip and WinRAR

6B-38 File Compression 763 KB on disk Compressed 157 KB

6B-39 Drive Interface Standards Interface –How the device is connected –Drive controllers allow transfer of data –Dictates transfer rate and access time

6B-40 Drive Interface Standards Enhanced Integrated Drive Electronics –EIDE –Generic term for drive controllers –Several names Fast IDE Advanced Technology Attachment (ATA) –Up to 2 devices per controller –Most computers have 2 EIDE controllers

6B-41 Drive Interface Standards Small Computer System Interface –SCSI –Higher transfer rates than EIDE –More than 40 devices per SCSI controller Computers may have several SCSI controllers –Many versions exist Versions are typically incompatible –Found in servers and workstations

6B-42 Drive Interface Standards USB and FireWire –External drives –Transfer rate is limited –Many devices can be connected

Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill Technology Education Chapter 6B End of Chapter