Secondary Storage

1
Secondary Storage

• Learning Objectives
• Identify the methods of magnetic tape and disk
  storage along with advantages and disadvantages.
• Discuss optical disk storage options, including
  advantages and disadvantages.
• Identify additional storage options and
  technology trends

2
Purposes of Secondary Storage

• Secondary Storage or long term storage of data
  outside the computers CPU referred to as
  non-volatile because the contents are not erased
  when the computer power is turned off.
• Encoding Systems
• Binary System
• Uses two options 0 and 1
• EBCDIC and ASCII

3
Tape Storage Media

• Sequential access
• Reel to Reel Magnetic Tapes
• Mainframe computers
• Tracks- Parallel Rows
• Nine rows
• Eight bits used to represent a character
• Ninth bit is call a parity bit for checking
• Magnetic Cartridges
• Micro computers/PCs

4
Tape Storage Media

• Sequential access is slow.
• Tape is ideal for overnight backup
• Cartridges have become very popular
• They hold large amounts of data in a small space
• Used by both Microcomputers and midrange systems
• more secure backup than disk

5
Magnetic Disk Storage Media

• Direct Access Storage Devices
• Read Write Heads on an Access Arm
• Information stores on sectors separated by tracks
• Sector
• a subsection of magnetic disk, used as part of
  the address to identify the location of data

• Floppy Disks
• 5¼ 360K to 1.2 MB
• 3½ 720k -1.4- 2.8
• Floppy Disks
• 5¼ 360K to 1.2 MB
• 3½ 720k -1.4- 2.8

6
Optical Disks

• Laser technology
• Longer shelf life
• Less susceptible to poor environmental conditions
• CD-ROMs
• WORMs
• Jukeboxes

• Ideal for archiving
• Information that doesnt need updating.
• Sale of Software Programmes
• Capacity
• 600MG

7
Trends and Developments

• High Capacity Magnetic Disks
• Zip
• Jazz
• Rewritable CDs
• Magneto optical technology.
• Data Compression
• PC Memory Cards
• DVD