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Memory and storage 3: secondary storage technologies

RAM is useful while a computer is running, but it is volatile and has limited capacity. Computers therefore need secondary storage for data, applications and files that must be kept.

By the end of this worksheet, you should be able to:

explain why secondary storage is needed
identify magnetic, optical and solid-state storage
distinguish a storage type from a device or medium
recognise examples of each technology
compare their broad characteristics without describing unnecessary internal components

Work through the explanation, checks and applications in order. Use the final challenge to connect several ideas.

1. Why secondary storage is needed

Secondary storage is non-volatile, so stored data remains when the power is switched off. It normally has a much larger capacity than primary storage and is used for long-term storage of:

user files
installed applications
the operating system

Secondary storage is not used only when RAM is full. Its ordinary purpose is long-term, non-volatile storage. Virtual memory is one specialised use of a section of secondary storage.

Multiple choice1 mark

What is the main reason a computer needs secondary storage?

ATo decode every CPU instruction
BTo provide non-volatile, long-term storage for data and programs
CTo replace RAM only when RAM becomes full
DTo display the user interface

2. Three common storage technologies

OCR requires you to recognise:

magnetic storage, such as a hard disk drive or magnetic tape
optical storage, such as a CD, DVD or Blu-ray disc
solid-state storage, such as an SSD, USB flash drive or memory card

Notice the language:

magnetic is a type of storage
a hard disk drive is a storage device
the disk inside it is the storage medium

Exam questions may ask specifically for a type, device or medium. Read the wording carefully.

Fill in the blanks4 marks

A hard disk drive commonly uses label 1 storage. A DVD is an example of label 2 storage. An SSD and a USB flash drive use label 3 storage. All three are forms of label 4.

cache
solid state
secondary storage
magnetic
RAM
optical

Multiple choice, several answers3 marks

Which three device-to-technology matches are correct? Select all that apply.

AHard disk drive: magnetic
BDVD: solid state
CUSB flash drive: solid state
DSSD: optical
EBlu-ray disc: optical

3. Magnetic storage

Common examples are hard disk drives and magnetic tape.

Magnetic hard disk drives commonly offer:

high capacity
a relatively low cost per gigabyte
suitable long-term storage in desktop computers or servers

They contain moving parts, so movement while operating can cause damage. They normally have slower access speeds than solid-state drives.

Magnetic tape can hold large backups or archives, but data is accessed in sequence, so it is not normally chosen for everyday rapid access.

4. Solid-state storage

Examples include SSDs, USB flash drives and memory cards.

Solid-state storage commonly offers:

fast access
no moving parts
low power use
good portability and resistance to movement

It usually costs more per gigabyte than magnetic storage. “No moving parts” does not mean that a device is impossible to damage or that it will last forever.

5. Optical storage

Examples include CDs, DVDs and Blu-ray discs.

Optical discs are commonly:

inexpensive to distribute
thin and easy to transport
lower in capacity and slower to access than many modern magnetic or solid-state devices
vulnerable to scratching or breaking

OCR does not require you to explain the internal component parts of these technologies. Concentrate on recognition, characteristics and suitable uses.

Multiple choice1 mark

Which statement is the most accurate broad comparison?

ASolid-state storage normally has fast access and no moving parts, but often costs more per gigabyte than magnetic storage
BOptical storage always has the highest capacity and fastest access
CMagnetic storage is volatile and loses files without power
DEvery solid-state device is impossible to damage

Written answer3 marks

Explain the difference between a storage type and a storage device. Give one linked example.

For example, connect the general technology to a named piece of hardware.

Students type their answer here.

Written answer4 marks

Compare a magnetic hard disk drive with a solid-state drive. Give two developed differences.

Use paired statements. Suitable areas include access speed, cost per gigabyte, moving parts, durability during movement or power use.

Students type their answer here.

Multiple choice1 mark

An exam question asks for one secondary storage device. Which answer best follows the instruction?

ANon-volatile
BSecondary
CMagnetic
DHard disk drive

Written answer6 marks

Challenge: a school technician says, “New computers use solid-state storage, so magnetic and optical storage have no useful purpose.” Evaluate this claim.

Consider more than speed. Discuss cost per gigabyte, capacity, portability, distribution, backup or archive uses, then reach a judgement.

Students type their answer here.

Closed-book review

Without looking back, complete:

Secondary storage is needed because...
One magnetic device is...
One optical medium is...
Two solid-state devices are...
HDDs commonly offer...
SSDs commonly offer...
Optical discs commonly offer...
A storage type differs from a device because...

Check that your answers use qualified comparisons rather than impossible claims such as “never fails”.