Published by Patrick Mutisya · 14 days ago
Understanding the different types of storage media is essential for selecting the right solution for a given need. The three main categories covered in the IGCSE ICT syllabus are magnetic, optical and solid‑state storage. Each has distinct characteristics, typical uses, advantages and disadvantages.
Magnetic storage uses the magnetisation of a surface to record data. It has been the dominant form of secondary storage for many decades.
| Characteristic | Typical Use | Advantages | Disadvantages |
|---|---|---|---|
| Medium: ferromagnetic coating on a rotating platter (hard‑disk) or a moving magnetic tape | Desktop PCs, laptops, servers, archival backup (tape) | High capacity for price, mature technology, large data‑transfer rates (HDD) | Mechanical parts prone to wear, slower access time than SSD, vulnerable to magnetic fields |
| Read/write method: magnetic heads that alter polarity of tiny domains | Random‑access storage (hard‑disk) and sequential access (tape) | Random access enables fast file retrieval on HDDs | Seek time and latency increase with platter size; tape requires winding |
| Form factors: 3.5‑inch, 2.5‑inch, 1.8‑inch, external USB enclosures, magnetic tapes (DAT, LTO) | Desktop storage, portable external drives, enterprise backup | Versatile physical sizes, easy to replace or upgrade | Physical size can limit portability; external drives need power source |
Optical media store data as pits and lands on a reflective surface that are read by a laser.
| Characteristic | Typical Use | Advantages | Disadvantages |
|---|---|---|---|
| Medium: polycarbonate disc with a metallic layer (CD, D \cdot D, Blu‑ray) | Software distribution, music/video media, archival storage | Read‑only versions are inexpensive; resistant to magnetic interference; long shelf life when stored properly | Limited rewrite cycles (especially CD‑R); lower capacity compared with HDD/SSD; slower data rates |
| Capacity: CD ≈ 700 MB, D \cdot D ≈ 4.7 GB (single‑layer), Blu‑ray ≈ 25 GB (single‑layer) | Home entertainment, backup of important files | Standardised formats, widely compatible with many devices | Physical discs can be scratched; data becomes unreadable if surface is damaged |
| Read/write method: laser of 780 nm (CD), 650 nm (D \cdot D), 405 nm (Blu‑ray) | Recordable media (CD‑R/W, D \cdot D‑R/W, BD‑RE) | Non‑contact reading reduces wear on the medium | Laser alignment required; older drives may not read newer formats |
Solid‑state devices store data in flash memory cells with no moving parts.
| Characteristic | Typical Use | Advantages | Disadvantages |
|---|---|---|---|
| Medium: NAND flash memory chips (SATA SSD, N \cdot Me PCIe SSD, USB flash drive, memory card) | Laptops, tablets, smartphones, high‑performance servers, portable storage | Very fast read/write speeds, low latency, silent operation, resistant to shock | Higher cost per gigabyte than magnetic, limited write‑endurance (though improving) |
| Form factors: 2.5‑inch SATA, M.2 (SATA or N \cdot Me), PCIe add‑in card, USB stick, SD card | Internal primary storage, external portable drives, camera storage | Compact size, low power consumption, no moving parts | Data retention can degrade if not powered for long periods (especially in cheap drives) |
| Interface: SATA III (6 Gb/s), PCIe 3.0/4.0 (up to 32 Gb/s), USB 3.2, UHS‑II for cards | High‑speed data transfer, gaming, video editing | Scalable performance with newer interfaces | Compatibility issues with older hardware lacking N \cdot Me support |
The table below provides a quick reference for choosing a storage medium based on common criteria.
| Criteria | Magnetic | Optical | Solid‑State |
|---|---|---|---|
| Typical Capacity (per unit) | 500 GB – 10 TB (HDD); 1 TB – 30 TB (Tape) | 0.7 GB – 25 GB | 128 GB – 8 TB |
| Cost per GB (approx.) | Low | Very low (read‑only) / moderate (recordable) | Higher |
| Access Speed | \overline{100} MB/s (HDD) – 300 MB/s (SMR) ; Tape is sequential | \overline{10} MB/s (CD) – 50 MB/s (D \cdot D) – 100 MB/s (Blu‑ray) | \overline{500} MB/s (SATA SSD) – >3000 MB/s (N \cdot Me) |
| Durability | Susceptible to shock, magnetic fields | Resistant to magnetic fields, but surface damage critical | Highly shock‑resistant, no moving parts |
| Typical Uses | Primary computer storage, enterprise servers, backup archives (tape) | Media distribution, long‑term archival, software install discs | Operating system drives, high‑performance applications, portable data carriers |