iGCSE Theory Unit 3 - backing up data

Section 3
Storage Devices and Media
Jon Spavin

Magnetic drum memory
Invented all the way back in 1932 (in Austria), it was widely used in the
1950s and 60s as the main working memory of computers. In the
mid-1950s, magnetic drum memory had a capacity of around 10 kB.

Above left: The magnetic Drum Memory of the UNIVAC computer.
Above right: A 16-inch-long drum from the IBM 650 computer. It had 40
tracks, 10 kB of storage space, and spun at 12,500 revolutions per minute.

The hard disk drive. The first hard disk drive was the IBM Model 350 Disk
File that came with the IBM 305 RAMAC computer in 1956. It had 50 24-inch
discs with a total storage capacity of 5 million characters (just under 5 MB).

Above: IBM Model 350, the first-ever hard disk drive.

The first hard drive to have more than 1 GB in capacity was the IBM 3380 in
1980 (it could store 2.52 GB). It was the size of a refrigerator, weighed 550
pounds (250 kg), and the price when it was introduced ranged from $81,000 to
$142,400.

Above left: A 250 MB hard disk drive from 1979. Above right: The IBM 3380
from 1980, the first gigabyte-capacity hard disk drive.

The floppy disc
The diskette, or floppy disk (named so because they were flexible), was invented
by IBM and in common use from the mid-1970s to the late 1990s. The first floppy
disks were 8 inches, and later in came 5.25 and 3.5-inch formats. The first floppy
disk, introduced in 1971, had a capacity of 79.7 kB, and was read-only. A read-
write version came a year later.

Above left: An 8-inch floppy and floppy drive next to a regular 3.5-inch floppy
disk. Above right: The convenience of easily removable storage media.

Magnetic tape
Magnetic tape was first used for data storage in 1951. The tape device was called
UNISERVO and was the main I/O device on the UNIVAC I computer. The effective
transfer rate for the UNISERVO was about 7,200 characters per second. The tapes
were metal and 1200 feet long (365 meters) and therefore very heavy.

Above left: The row of tape drives for the UNIVAC I computer. Above right:
The IBM 3410 Magnetic Tape Subsystem, introduced in 1971.

Section 3 – Storage Devices
• Backing up data

– What is Backing Up?
– Why do we back up?

• (3.1) Backing up data
– What is Backing up data?
• Copying of files and data to a different medium (disk, tape,
flash drive, etc,) in case of a problem with the main storage
device.
• Some backups are often stored in a different place to the
main storage.
– Why do we back up?
• Data could be lost
• Hackers could be responsible for the corruption or even loss
of data
• Backups are also made in case the file need to be used
elsewhere. The original file are then protected against
possible corruption or loss

(3.1) Backing up data
What is Backing up data?
• Copying of files and data
to a different medium.
– Can you identify at least
three different types
(disk, tape, flash drive,
etc,) in case of a problem
with the main storage
device.

•Some backups are often stored in a
different place to the main storage.
•Can you identify a number of
different places?

• (3.2) Types of Access
– Serial Access
• With this system, to access the data it is necessary to start at
the beginning and then access each piece of data in turn
until the required information is found.
– Direct Access
• This method is used with magnetic disks and with optical
media. The computer uses a key field to calculate where the
data has been stored.

(3.1) Types of Access
Types of Access?

• Serial Access
– With this system, to access the data it is
necessary to start at the beginning and
then access each piece of data in turn
until the required information is found.

•Direct Access

This method is used with magnetic
disks and with optical media. The
computer uses a key field to calculate
where the data has been stored.

• Backing storage media
– Internal or External
• Magnetic
• Optical
• Solid State

• Portable hard disk drives
• Floppy disk drives
• Magnetic tapes

How does the Hard Drive work?
• There's just a large shiny, circular
"plate" of magnetic material called a
platter, divided into billions of tiny
areas. Each one of those areas can be
independently magnetized (to store a
1) or demagnetized (to store a 0).
Magnetism is used in computer
storage because it goes on storing
information even when the power is
switched off. If you magnetize a nail, it
stays magnetized until you
demagnetize it. In much the same way,
the computerized information (or data)
stored in your PC hard drive or iPod
stays there even when you switch the
power off.

• http://www.youtube.com/watch?v=RQau2

• http://www.explainthatstuff.com/harddrive.html

What are the parts in a hard drive?

1. Actuator (compact electric motor that
moves the read-write arm).
2. Read-write arm swings read-write head
back and forth across platter.
3. Central spindle allows platter to rotate
at high speed.
4. Magnetic platter stores information in
binary form.
5. Plug connections link hard drive to
circuit board in personal computer.
6. Read-write head is a tiny magnet on
the end of the read-write arm.
7. Circuit board on underside controls the
flow of data to and from the platter.
8. Flexible connector carries data from
circuit board to read-write head
and platter.
9. Small spindle allows read-write arm to
swing across platter.

Hard Drives

Little and large: Here's the 30GB laptop hard-drive (shown in the other photos on
this page) next to a 20GB PCMCIA hard drive from an iPod. The two drives look
strikingly similar and work exactly the same way (both are made by Toshiba), but
the iPod drive is even more of a miracle of miniaturization!

Backing Storage Media
• All computer systems have come equipped with some form of
backing storage. When a user type data into a computer, the
information is stored temporarily on the RAM – however, this
information would be lost as soon as the computer was turned off.
Backing storage devices ensure the data is stored permanently and
can be used later.
– Either internal or External and one of three
types
• Magnetic
• Optical
• Solid State

Magnetic
• Fixed Hard Disk
• Portable Hard Disk
• Floppy Disk Drive
• Magnetic Tapes

Optical

• CD-ROM & DVD-ROM
• CD-R & DVD-R
• CD-RW & DVD-RW
• DVD-RAM
• Blu-ray disks

Solid State Backing Store
• Memory sticks/pen drives
• Flash memory pens

How much space do you think you might
have on the following devices?
• Internal Hard Drive = 20Gb - 1tb
• USB Sticks
– Solid State
• External Hard Drives
– Magnetic
– Solid State

• Magnetic tapes

What types are the following
storage devices?
• Fixed Hard Disk
• Portable Hard Disk
• Magnetic tapes
• CD-ROM & DVD ROM
• CD-RW & DVD-RW
• DVD RAM
• Blue-ray Disks
• Solid State backing store
• Memory sticks/pen drives
• Flash memory cards

Use: Used in home video
consoles?
A. Fixed Hard Disk
B. Portable Hard Disk
C. Floppy disk drives
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks
I. Solid State backing store
J. Memory sticks/pen drives
K. Flash memory cards

Use: Used as a security device
– dongle to prevent piracy?
A. Fixed Hard Disk
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

Use: transporting files between
computers or as a back up
A. Fixed Hard Disk
store?
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

Which storage device would you choose
for : using in MP3 players to store music
files?
A. Fixed Hard Disk
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

Which storage device would you choose for:
recording radio & television programs but can be
recorded over again and again?
A. Fixed Hard Disk
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

Which storage device would you choose for :
where manufacturers store music files and
software like computer games?
A. Fixed Hard Disk
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

Which storage device would you
choose for : doing home recordings of
music and films?
A. Fixed Hard Disk
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

Which storage device would you choose for:
batch processing of clearing bank
cheques?
A. Fixed Hard Disk
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

Which storage device would you choose
for : storing the computers operating
system?
A. Fixed Hard Disk
D. Magnetic tapes
E. CD-ROM & DVD ROM
F. CD-RW & DVD-RW
G. DVD RAM
H. Blue-ray Disks

iGCSE Theory Unit 3 - backing up data

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