Chapter 6A Types of Storage Devices Describing Storage Devices Store data when computer is off Two processes Writing data Reading data 2 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 3 1
Magnetic Storage Devices Most common form of storage Hard drives, floppy drives, tape All magnetic drives work the same 4 Magnetic Storage Devices Floppy Disk Hard Disk Tape 5 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 6 2
Data Retrieval 7 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 8 Tracks and Sectors 9 3
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 10 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 Practically obsolete 11 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 12 4
Illustrated Hard Disk 13 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 14 Magnetic Storage Devices Tape drives Best used for Infrequently accessed data Back-up solutions Slow sequential access Capacity exceeds 200 GB 15 5
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 16 Optical Storage Devices DVD-ROM Digital Video Disk Use both sides of the disk Capacities can reach 18 GB DVD players can read CDs 17 Recordable Optical Technologies CD Recordable (CD-R) Create a data or audio CD Data cannot be changed Can continue adding until full 18 6
Recordable Optical Technologies CD ReWritable (CD-RW) Create a reusable CD Cannot be read in all CD players Can reuse about 100 times 19 Recordable Optical Technologies Photo CD Developed by Kodak Provides for photo storage Photos added to CD until full Original pictures cannot be changed Hardly used anymore 20 Recordable Optical Technologies DVD Recordable Several different formats exist None are standardized Allows home users to create DVDs Cannot be read in all players 21 7
Recordable Optical Technologies DVD-RAM Allow reusing of DVD media Not standardized Cannot be read in all players 22 Solid State Devices Data is stored physically No magnets or laser Very fast 23 Solid State Devices Flash memory Found in cameras and USB drives Combination of RAM and ROM Long term updateable storage 24 8
Solid State Devices Smart cards Credit cards with a chip Chip stores data Eventually may be used for cash Hotels use for electronic keys 25 Solid State Devices Solid-state disks Large amount of SDRAM Extremely fast Volatile storage Require battery backups Most have hard disks copying data 26 Chapter 6A End of Chapter 9
Chapter 6B Measuring and Improving Drive Performance Drive Performance Average access time Also known as seek time Time to find desired data Measured in milliseconds Depends on two factors RPM Time to access a track Hard drive between 6 and 12 ms CD between 80 and 800 ms 29 Drive Performance Data transfer rate How fast data can be read Measured in Bps or bps 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 30 10
Data Transfer Rate 31 Optimizing Performance Disk optimization Handled by operating system tool Routine disk maintenance Optimization should be run monthly 32 Optimizing Performance Clean up unnecessary files Delete temp files Uninstall unused programs Delete obsolete data files Files should be cleaned weekly 33 11
Optimizing Performance Scan a disk for errors Bad spots on the media Find and fix the error Move data to a good spot Mark the spot as bad Disks should be scanned monthly 34 Optimizing Performance Defragment a disk Files fragment when resaved Fragmented files load slower Defragment puts the fragments together Disks should be defragged monthly 35 Defragment 36 12
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 37 File Compression 763 KB on disk Compressed 157 KB 38 Drive Interface Standards Interface How the device is connected Drive controllers allow transfer of data Dictates transfer rate and access time 39 13
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 40 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 41 Drive Interface Standards USB and FireWire External drives Transfer rate is limited Many devices can be connected 42 14
Chapter 6B End of Chapter 15