Storage Media

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Lesson 4 - SPring Term 2 - Storage Media


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🎯 Learning Objectives

  • LO1: We are learning how magnetic storage functions
  • LO2: We are learning how optical storage functions
  • LO3: We are learning how solid state drives function

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Why do we need secondary storage?

  • As we have already learned, primary storage is volatile --- (What does this mean?)
  • As a result, we need to permanently store data and programs somewhere non-volatile
  • This is so we can access them at a later point

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Secondary Storage Types

Today we will explore three types of secondary storage

  • Magnetic
  • Solid State
  • Optical

Can you identify each on the image below?

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Magnetic Storage (Hard Disk Drives)

  • Magnetic hard disk drives are made from spinning metal platters
  • Each platter is coated in magnetic particles
  • A (+) particle is a binary (1)
  • A (-) particle is a binary (0)
    •

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The Read/Write Head

A special component called the read/write head passes over the surface of each platter.

As it does, it can carry out either of the actions below:

  • Read: where it detects the pole of each particle and sends either a (1) or (0) back to the computer
  • Write: where it changes the pole of the particle, to change the data on the disk

📝 Independent Activity

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📝 Activity 1 - Magnetic Storage

Instructions:

Explain how magnetic storage works. In your explanation, refer to:

  • The platter
  • The read/write head
  • magnetic particles

Extension Task

Magnetic hard disk drives have moving parts.

Find out why this makes them problematic

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Optical Storage

  • Optical storage is made from plastic disks that contain a thin sheet of metal foil
  • The metal foil is perforated with tiny metal holes called pits

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Optical Read Head

A special component called the optical read head passes over the surface of an optical disk.

As it passes over it shines a laser at the surface of the disk.

When it does this, one of two things can happen:

  • The laser bounces off the surface of the disk
    • This then gets received by a lens
    • A binary (1) is recorded by the computer
  • The laser lands in one of the pits
    • The laser doesn't get received by the lens
    • A binary (0) is recorded by the computer

🧠 Consolidation Activity

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Extension Activity

Research and report back on other types of magnetic storage we used in the past

Investigate:

  • How much they could store
  • What they were used for

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Solid State Drives

Solid state drives use the same "Flash" technology as SD cards and USB thumb drives

Flash technology allows for data to be stored on microchips; even without a steady power supply!

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Electron Pools

The chips are full of billions of microscopic electron pools

Each electron pool can be either filled with electrons (through a special charging process) or be empty.

To read the data, electronic current is passed through each of these pools:

  • If a pool is full of electrons the current is repelled and a binary (0) is read by the computer
  • If a pool is empty, the current enters and takes longer to leave, causing the computer to read a binary (1)

📝 Independent Activity

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📝 Activity 2 - Solid State Drives

Answer the following questions:

(a) What is a solid state drive made out of?


(b) What will cause the computer to read a binary (1)?


(c) What will cause the computer to read a binary (0)?

✅ Plenary Activity

📝 MWB Reflection Task

Open the mini-whiteboard app in a new tab

Your teacher will start with these leading questions:

  • What is the part of a hard disk drive covered in magnetic particles?
  • What happens when the laser points into a pit?
  • What are electron pools and how do they work?
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