Shelly Cashman Series Discovering Computers

1
Shelly Cashman SeriesDiscovering Computers

• Storage

2
OBJECTIVES

• Define storage
• Identify the major storage devices
• Explain how data is stored on floppy disks and
  hard disks
• Explain how data compression works
• Explain how data is stored on optical disks such
  as CD-ROMS

3
CHAPTER 5 PRIMARY OBJECTIVES (cont.)

• Explain how magnetic tape storage is used with
  computers
• Describe other forms of storage PC-Cards, RAID,
  and mass storage devices
• Describe how special-purpose storage devices,
  such as smart cards, are used

4
WHAT IS STORAGE?

• Stores programs and data
• Nonvolatile/volatile
• Writing/recording data
• Reading data
• Used as input and output devices
• Variety of devices
• Storage Medium
• Access Time
• Capacity

Click to see Figure 5-1
5
Memory Versus Storage
Memory (RAM)
Hard Disk
Compact Disc
Floppy Disk
Tape
p. 7.4 Fig. 7-4
6
Floppy Disks

• What are the parts of a floppy disk?

• A thin circular flexible film is enclosed between
  two liners
• A piece of metal called a shutter covers an
  opening to the recording surface

Click to view Web Link then click Floppy Disks
p. 7.6 Fig. 7-5
7
MAGNETIC DISK STORAGE

• Floppy disks (diskette)
• Formatting Preparing a floppy disk for use
• Sides
• Track
• Sector / Track
• Bytes / Sector
• Cluster
• Write-protect window

Click to see Figure 5-6
8
MAGNETIC DISK STORAGE

• Floppy disks (diskette)
• Formatting Preparing a floppy disk for use
• Sides - 2
• Track - 80
• Sector / Track - 18
• Bytes / Sector - 512
• 2 80 18 512 1.44MB
• Cluster
• Write-protect window

Formatting a Disk Video
9
Floppy Disks

• What are tracks and sectors?

• Track a narrow recording band that forms a full
  circle on the surface of the disk
• Pie shaped sections break the tracks into small
  arcs called sectors
• A sector can store up to 512 bytes of data
• A typical floppy disk stores data on both sides
  of the disk

80 tracks per side X 18 sectors per track X 2
sides per disk X 512 bytes per sector
1,474,560 bytes
p. 7.8 Fig. 7-8
10
MAGNETIC DISK REMOVABLE STORAGE

• High Capacity disks
• SuperDisk
• 120 240 MB
• HiFD
• 200 MB
• Zip Disk
• Special drive
• 100 250 MB

• SuperDisk and HiFD
• 200 Mb
• Use a 3.5 Drive
• Downward compatible

Click to see Figure 5-9
11
MAGNETIC DISK STORAGE

• Hard disks
• One or more rigid platters
• Fixed disks or direct-access storage devices
  (DASD) on minicomputers and mainframes
• Magnetic HD
• 40 120 GB storage
• Optically Assisted HD
• 250 GB

Click to see Figure 5-11
12
MAGNETIC DISK STORAGE

• Hard disks
• Storing data on a hard disk
• Disks rotate at high speeds
• Read/write heads float on a cushion of air
• Head crash
• Partitions
• Disk cache
• Disk Cache controller
• IDE / EIDE hard disk controllers
• 4 disk 137 GB each
• SCSI hard disk controllers

How a Hard Disk Stores Data Animation
13
How a Hard Disk Works
14
Hard Disks

• What is a cylinder?

• The location of a single track through all
  platters
• A single movement of the read/write head arms can
  read all the platters of data

Click to viewanimation
p. 7. 11 Fig. 7-14
15
Hard Disks

• What is a head crash?

• Occurs when a read/write head touches the surface
  of a platter
• The platters of the hard disk rotate at a high
  rate of speed while the computer is running
• The spinning creates a cushion of air that floats
  the read/write head above the platter

hair
read/write head
dust
smoke
gap
p. 7. 12 Fig. 7-15
platter
16
Hard Disks

• How does access time compare for a hard disk and
  a floppy disk?

• A hard disks access time is significantly faster
  than a floppy disk
• The hard disk spins much faster than a floppy
  disk
• A hard disk spins constantly, while a floppy disk
  starts spinning only when it receives a read or
  write command

Click to view Web Link then click Hard Drives
p. 7. 12
17
Hard Disks

• What is a disk cache?

• A portion of memory that the processor uses to
  store frequently accessed items

• A cache controller manages cache and thus
  determines which items cache should store

p. 7. 12 Fig. 7-16
18
Hard Disks

• What is a partition?

• You can divide a formatted hard disk into
  separate areas called partitions
• Done by issuing a special operating system
  command
• Each partition functions as if it were a separate
  hard disk drive

p. 7. 12
19
Removable Disks

• Use removable hard disk called cartridges
• Peerless
• 20 GB
• Jaz
• 2 GB

20
OTHER TYPES OF STORAGE DEVICES

• RAID storage systems
• Redundant array of inexpensive disks
• RAID level 1 - disk mirroring
• RAID levels beyond 1- striping
• Better than SLEDs - single large expensive disks
• Faster
• Reduced risk of data loss
• http//www.peripheralstorage.com/snap/raid0.html

21
Hard Disks

• What is RAID?
• Redundant array of independent disks
• A type of hard disk system that connects several
  smaller disks into a single unit that acts like a
  single large hard disk
• More reliable than a traditional disk system but
  quite expensive

p. 7.14 Fig. 7-18
22
(No Transcript)
23
Maintaining Your Disk

• System Tools
• Backup
• Disk Cleanup
• Disk Defragmenter
• Schedule Tasks
• System Restore

24
Internet Hard Drives

• Online Storage
• Free or Fee based
• Benefits
• Data Accessibility
• Share Data
• Off site backup

25
Compact Discs (Optical Disc)

• CD-ROM (compact disk read-only memory)
• 650MB 1GB of information

Click to see Figure 5-18
26
(No Transcript)
27
(No Transcript)
28
CD-ROM AND OPTICAL DISKS

• CD-ROM (compact disk read-only memory)
• 650MB 1 GB of information
• Read Only / Read-Write
• Speed - transfer rate 1x 150 KB
• Multisession
• Photo CD
• CD-ROM, CD-R, CD-RW
• DVD (digital video disk)
• 4.7 Gigabytes - 17 Gigabytes
• DVD-ROM, DVD-R, DVD-RW

29
DVD Capacity
30
MAGNETIC TAPE

• Thin ribbon of plastic
• Sequential storage

Click to see Figure 5-19
31
MAGNETIC TAPE

• Cartridge tape devices
• Magnetic recording tape in a small, rectangular
  plastic housing
• Automatic loaders

Click to see Figure 5-21
32
MAGNETIC TAPE

• Reel-to-reel tape devices
• Large computer systems
• Two reels

Click to see Figure 5-22
33
MAGNETIC TAPE

• Storing data on magnetic tape
• Read/write head that can read or write magnetic
  patterns on the tape representing bits
• QIC Quarter Inch Cartridge - up to 5GB
• DAT Digital Audio Tape - up to 24GB
• DLT Digital Linear Tape - up to 40GB
• Tape density - bits per inch (bpi)

34
Enterprise Storage Systems

• Availability
• CD-ROM Juke Boxes
• Network Attached Storage
• Storage Area Network
• Protection
• RAID
• Backup
• Internet

35
Enterprise Storage Systems

• What is an enterprise storage system?

• A strategy that focuses on the availability,
  protection , organization, and backup of storage
  in a company
• Goal is to consolidate storage so operations run
  as efficiently as possible

p. 7.27 Fig. 7-34
36
OTHER TYPES OF STORAGE DEVICES

• PC cards
• Very small
• Most often used with portable computers
• Can store more than 300 MB of data

Click to see Figure 5-24
37
OTHER TYPES OF STORAGE DEVICES

• Special-purpose storage devices
• Memory buttons
• Smart cards
• Optical memory cards
• Microfilm / Microfiche

Click to see Figure 5-30
38
Life Expectancies

• Tape
• 2 5 years guaranteed
• 20 years possible
• CD
• 5 years guaranteed
• 50 years possible
• Microfilm
• 100 years guaranteed
• 200 years possible

39
COMPUTERS AT WORK

• HSM Hierarchical storage management
• Online storage
• Near-line storage
• Off-line storage
• Shelf storage
• Placeholders

Click to see Figure 5-32
40
IN THE FUTURE

• Holographic storage
• Three-dimensional image
• Laser technology
• Obstacles
• Size
• Temperature

Click to see Figure 5-33
41
Storage Complete