Secondary Storage Technologies

At A-Level you need a thorough understanding of secondary storage — not just what the technologies are, but how they work at a physical level, their performance characteristics, and the trade-offs between them.

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Why Secondary Storage?

Main memory (RAM) is volatile — it loses its contents when the power is switched off. Secondary storage is non-volatile and retains data permanently (until deliberately erased). It is used for long-term storage of programs and data.

Secondary storage is also much cheaper per gigabyte than RAM, but significantly slower.

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Magnetic Storage — Hard Disk Drives (HDDs)

How HDDs Work

An HDD stores data on one or more spinning platters coated with a magnetic material. Data is read and written by a read/write head that floats just above the platter surface.

        Spindle
          │
    ┌─────┼─────┐
    │     │     │    ← Platters (spinning discs)
    │     │     │
    └─────┼─────┘
          │
    Read/write head ───── Actuator arm