3.4c Secondary Storage - adv and dis

Question 1

What is secondary storage?

Answer 1

Secondary storage is the memory in which the computer can store the data or instructions which are NOT currently in use.
Not all computer systems use secondary storage.
E.g.
Hard Disk Drive (HDD)
Solid State Drive (SSD)
Compact Disk (CD)

Question 2

What is Primary storage

Answer 2

Primary storage is the memory in which the computer can store the data or instructions that are currently in use.
The two main types of primary storage are:
Random Access Memory (RAM)
Read-Only Memory (ROM)

Question 3

What is solid state storage sometimes referred to as?

Answer 3

Flash storage or Flash Memory

Question 4

Where does flash memory store data?

Answer 4

Flash memory stores the value of each bit in a semi-conductor chip

Question 5

How can data be accessed in Flash memory?

Answer 5

Data can be accessed randomly. This means that any piece of data can be accessed in a constant amount of time.
This is achievable because there are no moving parts.

Question 6

How reliable is magnetic storage?

Answer 6

The HDD has moving parts.
Although the HDD is generally reliable, any device with moving parts will be subject to wear-and-tear.
HDDs can also be damaged by shocks. They are not robust.

Question 7

What are the pros and cons of magnetic storage?

Answer 7

Pros:
Good Reliability
High Capacity - up to several terabytes per device
Low Cost per gigabyte - magnetic tape is the cheapest, but hard disk is very low as well.

Cons:
Hard disk has mechanical moving parts, so less rugged than solid state storage.
Data can be lost near strong magnetic fields,
Data read / write is not as fast as flash technology

Question 8

Why does magnetic storage have low speed?

Answer 8

Magnetic media needs a high number of moving parts.

The high number of moving parts make magnetic media slow to access.

Question 9

Why does magnetic storage have good reliability?

Answer 9

Magnetic media is reliable and tends to last for a long time.
Magnetic media is not robust, and tends to break on impact or during vibrations.

Question 10

Why does magnetic data have a high capacity of data storage?

Answer 10

Magnetic media can store a large quantity of data in a compact way.
This makes them a popular choice for archives as well as home computers

Question 11

What are some examples of Magnetic storage?

Answer 11

HDDs
Hybrid Drives
Magnetic tapes

Question 12

What is optical storage?

Answer 12

Optical storage uses laser light to retrieve data from the surface of optical media. Optical storage is often used to deliver multimedia content such as video

Question 13

What does a land represent, and what does a pit represent?

Answer 13

The lands represent 1 and the pits represent 0 in binary computing. (In optical storage)

Question 14

How are bits stored in optical storage?

Answer 14

Each 1 or 0 (value of a bit) is represented as a microscopic hole (called a pit) or a flat surface (called a land) on the surface of the disk

Question 15

How is data accessed in optical storage?

Answer 15

A laser is shone on the disk surface.
If the laser hits a land, it will be reflected into a sensor.
If the laser hits a pit, then it will be reflected elsewhere.
These can be used to represent our 1 and 0

Question 16

What are the pros and cons of optical storage?

Answer 16

Pros:
Low Cost (if less than 10gb needs to be stored per media item, not if terabytes needed )
Reliable - It is Waterproof and Shockproof
Good Capacity

Immune to magnetic fields
Very portable compared to hard disk
Ideally sized (5-50gb for storing movies and videos - why they were first created)

Cons:
Not Robust
Low capacity per disk
Slow Access times

Not as portable as flash media
Slow to write (burn) and much slower than hard disk to access
Easily scratched
Cannot write over stored data

Question 17

What are the three main types of optical storage?

Answer 17

Blue-Ray Disks (BD)
Compact Disk (CD)
Digital Versatile Disk (DVD)

Question 18

What are the three Optical Media standards?

Answer 18

Read-Only Media (ROM)
Write-Once (R)
Re-writable (RW)

Question 19

What is Read-Only Media?

Answer 19

A CD-ROM, DVD-ROM, or BD-ROM is a disk which can be read only.
The manufacturer writes the initial data, and this cannot be changed.
This is often used in content distribution so that people cannot accidentally overwrite the content.

Question 20

What is Write-once media?

Answer 20

A CD-R, DVD-R, or BD-R is a disk which can be written once by the user at home.
Once the user has written data to the disk, they cannot overwrite it.

Question 21

What is Re-Writable media?

+ when can be used

Answer 21

A CD-RW, DVD-RW, or BD-RW is a disk which can be overwritten whenever the user would like to.
These are often used for backups which might need to be updated in the future

Question 22

Solid state media (Flash) - adv and dos

Answer 22

Adv:

• very portable in the form of SD memory cards and USB memory sticks
• large capacity, especially in the form of a solid state drive
• Very tough and rugged as it has no moving parts unlike a hard disk
• Faster than hard disk as no mechanical parts need to be moved to read / write data.
• Solid State Drives are silent unlike hard disks

Dis:

• Solid State Drives are expensive compared to a hard disk of similar capacity.
• Less durable than a hard disk as it has a limited number of erase \ write cycles - maybe a 100,000 cycles before it wears out.