1. Chapter 8
Secondary Storage

2. Competencies (Page 1 of 2)
Distinguish between primary & secondary storage
Describe the traditional floppy disk and compare it to high capacity floppy disks
Compare internal hard disks, hard-disk cartridges, and hard-disk packs
Page 210

3. Competencies (Page 2 of 2)
Describe ways to improve hard-disk operations, including disk caching, redundant arrays of inexpensive disks, and data compression and decompression
Discuss the different types of optical disks; mass storage
Describe solid-state storage, Internet drives, and magnetic tape
Page 210

4. Storage RAM Primary storage Secondary storage
Volatile
Temporary
Secondary storage
Nonvolatile
Permanent
Secondary storage characteristics
Media
Capacity
Storage devices
Access speed
Secondary storage permanently saves information for future use; to share information with others; to modify at later date
Secondary storage is nonvolatile – stores programs and data as opposed to temporary storage (RAM)
Characteristics include:
Media or medium – actual physical materials that holds the data and programs
Capacity – measures how much a particular storage medium can hold
Storage devices – hardware that reads data and programs from storage media (most also write to storage media)
Access speed or access time – measures the amount of time required by the storage device to retrieve data and programs
RAM
Page 212

5. Secondary Storage Devices
Most desktop microcomputer systems have floppy disks, hard disks, and optical disk drives
Floppy disk – inexpensive and removable
Optical disks – large storage capacity
Hard disk – large storage capacity and fast retrieval times
Page 212

6. Traditional Floppy Disk
Also known as:
Diskettes
Floppies
Portable storage media
Floppy disk drives (FDD)
Insert Art Work top of page 213
Floppy disks are removable storage media. Today’s standard is 1.44 MB. Data recorded in rings called called tracks; tracks divided into wedge-shaped sections called sectors
Most disks manufactured currently preformatted w/tracks and sectors
While called floppy, actually pieces of flat Mylar rotating within a hard plastic jacket
The bits of data are represented by the presence or absence of magnetic charges
Storage capacities range from 360 KB to 1.44 MB
Write-protect notch or window to prevent inadvertent erasure or write-over
Density refers to how tightly the bits can be packed next to one another; common density is 2HD
A shutter on the disk slides to the side to expose the recording surface
Labels provide an area to write or document the contents of the disk
Page 212

7. High Capacity Floppy Disks
Known as a floppy-disk cartridge
Require special disk drives
Three well known types
Zip disks
HiFD disks
SuperDisks
Zip disks – usually manufactured by Iomega; 100 MB, 250 MB, or 750 MB worth of storage; requires own drive
HiDF disks – usually manufactured by Sony Corp; 200 MB or 750 MB capacity
Biggest advantages: can use HiDF disk in floppy drive; popular with notebooks
Super disks – usually manufactured by Imation; 120 MB or 240 MB capacity; SuperDisk disk drives can use standard floppy disks
Zip disks – 100 MB, 250 MB or 750 MB
HiFD disks MB or 720MB
SuperDisks – 120 MB or 240 MB
Page 214

8. Hard Disks Use thicker, metallic platters for storage
Faster than a floppy diskette
Large capacity
Sensitive instruments
There are three types of hard disks:
Internal
Hard-disk cartridge
Hard-disk pack
Composed of metallic rather than plastic disks
Platters – rigid metallic, stacked one on top of another
Fast information storage and retrieval
Read-write head is inch above surface
An internal hard disk is also known as a fixed disk
Page 215

9. Materials that Cause a Head Crash
Head crash is a disaster for a hard disk
Head crashes occur when the read-write head contacts with the disk surface or with particles on the disk's surface
Head crashes are now rare
A smoke particle, human hair, or fingerprint could cause a head crash
Return
Page 215

10. Internal Hard Disk Located inside system unit Known as a fixed disk
Designated as the C drive
Advantages over floppies
Access speed
Capacity
Located inside the system unit; also known as fixed disk
Used for storing the operating system, other programs, and large data files
You should perform routine maintenance and periodically backup all important files
Page 215

11. Optical Disks Compact Permanent storage Laser beams reflect off pits
Two common types CD
DVD
Use laser technology. CD and DVD are optical disk formats.
Compact, high capacity form of permanent storage (up to 17 gigabytes of data)
Laser beam writes by creating a pattern of pits (holes) and lands (flat areas) to encode data bits
Laser beams reflect off the pits and lands to read the data
Optical disks come in many different sizes
Most common is 4 ¾ inches
Stored in a protective case called jewel boxes
Page 219

12. Compact Disc Optical format From 650 MB to 1 GB capacity
Rotation speeds vary
Types
Read only: CD-ROM
Write once: CD-R
Rewriteable: CD-RW
Picture CDs and Photo CDs
CD stands for compact disc
Standard on most computers; can store from 650 MB up to 1 GB
Speed determines how fast data can be transferred
Read only: CD-ROM
Commercial music CD
Read only means it cannot be written on or erased
Used to distribute large databases and references
Write once: CD-R (CD-recordable)
Known as burners
Used to archive data or to record music downloaded from the Internet
Rewriteable: CD-RW
Known as erasable optical disks
Can be changed
Used to create and edit multimedia presentations
Picture CDs and Photo CDs
Special format developed by Eastman Kodak to store digital images
Two types: Single-session or multisession
Ideal for use as permanent data archives for essential company information
Page 219

13. Digital Versatile Disc
Digital Versatile Disk or Digital Video Disk (DVD)
Similar to CDs, but can store more data
Types
Read only: DVD-ROM
Write once: DVD+R; DVD-R
Rewritable: DVD+RW; DVD-RW; DVD-RAM
DVD-ROM
Known as DVD players
Used for videos
DVD-R and DVD+R
Two competing write once formats
Write once format
Used to create permanent archives for large amounts of data and to record videos
DVD-RAM or DVD-RW – rewritable version
DVD-RW
DVD+RW
DVD-RAM
Each format has a unique way of storing data; older DVD players can’t read all formats but the new DVD players can
Rapidly replacing the CD rewritable drives
Use to store video from camcorders and developing large multimedia presentations that include extensive graphics and video
Page 220

14. Other Types of Secondary Storage
Solid-state storage
Internet hard drives
Magnetic tape
Solid-state storage
No moving parts
Reliable, but expensive
Internet hard drives
Low cost
Flexibility to access information from any location using the Internet
Slower access speed
Magnetic tape
Slower sequential access
Stores data and programs
Used for making backups of data
Page 221

15. Solid-State Storage Flash memory cards Key chain hard drives
Widely used in notebook computers
Used to record MP3 music files
Key chain hard drives
Key chain flash memory devices
Connects to a USB port
Key chain hard drives have recently been introduced
Very compact
Worn as a necklace or on a key ring
Connect to a USB port
Predicted that they will replace the floppy disk for transporting data
Capacities up to 1 GB
Return
Page 221

16. Internet Hard Drives Known as i-drive or online storage Return
These are Web sites that provide storage space
Not used for storing highly personalized or sensitive information
Return
Page 224

17. Magnetic Tape External storage Provides sequential access
Information stored in sequence
Slower than disks which provide direct access
Magnetic tape streamers or tape cartridges used by both mainframes and microcomputers
Sequential access because they have to be fast forwarded or rewound before a specific location can be reached
A common sequential access method of permanent storage method
Common form of data backup in companies with larger computer systems; magnetic disk offer fast, direct access to data programs
Two forms of tape storage
Magnetic tape streamers
Backup tape cartridge units used with microcomputer systems
Capacities range from 120 MB to 5 GB
Return
Page 225