1.4 Secondary Storage

Question 1

What is secondary storage?

Answer 1

Secondary storage is storage that is non volatile and can usually be removed and put into another computer system

Question 2

Can secondary storage be accessed by the CPU?

Answer 2

No

Question 3

What are the uses of secondary storage?

Answer 3

• Programs and data are stored here
• Blu-rays may be used to distribute films
• Memory sticks may be used to transport data from one place to another
• Magnetic tape or external hard drives may be used for backup
• SD cards can be used for additional storage on cameras and smartphones; this is used for music, video and photos

Question 4

Secondary storage devices:

Answer 4

• Hard Disk Drive (HDD)
• Solid State Drive (SDD)
• Offline secondary storage

Question 5

Offline secondary storage devices:

Answer 5

• Compact Disk (CD)
• Digital Versatile Disk(DVD)
• Blu-ray
• Flash Memory
• SD cards
• Removable HDD or SDD
• Magnetic Tape

Question 6

Storage methods

Answer 6

• Magnetic:
  Mechanical parts move over the disks surface to read and write data magnetically, or a drive head reads a magnetic tape
• Optical:
  Lasers read and write data using light
• Solid State:
  Data is recorded onto solid memory chips without any moving parts

Question 7

Magnetic disk basic features

Answer 7

• Disk contains concentric circles called tracks
• Each track is divided into sectors
• Disk heads mounted on mechanical arms read and write data
• A disk with a solid platter is a ‘hard’ disk
• Soft plastic disks are known as ‘floppy’ disks

Question 8

Hard disks components

Answer 8

• Magnetic platter contains data
• Drive read / write head reads data on the drive
• Actuator moves the read / write arm
• Drive spindle rotates

Question 9

Magnetic storage features:

Answer 9

• Fixed magnetic hard disks are still used in many PCs and laptops
• Very large capacity (up to 6gb or more)
• Very cheap form of storage
• Portable hard disks can be connected to a computer via a USB port
• They are used for backing up or transporting data-

Question 10

Magnetic advantages:

Answer 10

Cheap, large storage capacities, relatively fast read and write speed

Question 11

Magnetic disadvantages:

Answer 11

Lots of mechanical parts, durability issue, sealed unit due to disk head and platter precision and not very portable

Question 12

Magnetic uses:

Answer 12

Personal computers, storage of large quantities of data

Question 13

Magnetic capacities:

Answer 13

500GB - 12TB or greater

Question 14

Optical storage basic features:

Answer 14

• Data is stored as pits and lands burnt or pressed into a spiral track circulating outwards from the centre
• A laser beam passes over the pits and lands the level of reflection is measured
  From the signal, 0s and 1s can be derived

Question 15

Optical advantages:

Answer 15

Cheap, very easily portable, takes up little space physically

Question 16

Optical disadvantages:

Answer 16

Less storage capacity compared to other types
Easily damaged / scratched, requires a CD reader
Slow write speeds

Question 17

Optical uses:

Answer 17

Songs, videos and other multi-media storage, backup and archiving of data

Question 18

Optical capacities:

Answer 18

• CD ROM; up to 720MB
• DVD; up to 8.4GB (dual layered disk)
• Blu-Ray; up to 50GB (dual layered disk

Question 19

CD vs Blu Ray

Answer 19

Blu ray can hold more space because it has a smaller pits and lands which allow it to store more data compared to CD which has bigger pits and lands. Also the wave length is larger

Question 20

SSD basic features:

Answer 20

• SSD disks use non-volatile flash memory to store information
• Very fast read / write speeds as it doesn’t need to wait for a disk to spin to the correct location and an arm to move
• No mechanical or moving parts meaning these disks are very durable

Question 21

How flash memory works:

Answer 21

• Large electric current used to force electrons through a barrier and trap them on the other side
• They remain on the other side until ‘flashed’ with a new current

e.g
Trapped (charged) or not trapped = 0 or 1

Question 22

SSD advantages:

Answer 22

Highly durable, no moving parts, very fast read and write speeds, no noisy fan or drive arm, faster start up times

Question 23

SSD disadvantages:

Answer 23

More expensive than magnetic hard disks, similar storage capacity as magnetic hard disks

Question 24

SSD uses:

Answer 24

Higher end computers, laptops, smartphones and tablets

Question 25

SSD capacitites:

Answer 25

100GB to 16TB

Question 26

Flash memory:

Answer 26

Low cost, portable, no moving parts, durable

Can be used on offline devices such as cameras, mobile phones and USB memory sticks

Question 27

Capacity meaning:

Answer 27

How much data can be stored

Question 28

Speed meaning:

Answer 28

The rate (usually in MB/s) at which data can be read or written

Question 29

Portability meaning:

Answer 29

How easy is it to carry

Question 30

Durability meaning:

Answer 30

How fragile is the device? How can it cope in different temperatures or scenraios?

Question 31

Reliability meaning:

Answer 31

How likely is the data (or some of it) to be lost?

Question 32

Cost meaining:

Answer 32

What is the cost of the device? How much is it to store 1 MB of data?

Question 33

Do different storage devices have a range of storage capacities?

Answer 33

Yes, in general, a higher capacity will allow greater data storage

Question 34

When you know how much data you need to store, you can decide which storage devices would be most appropriate?

Answer 34

Use the advantages and disadvantages to decide which storage device is the best to use and explain why

Question 35

Calculating data capacity:

Answer 35

Knowing the capacity required will enable us to make an informed decision as to which device to use.

Question 36

How much storage would we need if we had 5000 photos and each photo has a file size of 10MB?

Answer 36

5000 x 10 = 50000 MB which is 5GB

A suitable storage device to store this would be Blu Ray for portability or SSD for faster access times and write speeds