Know and understand characteristics, uses, media, advantages and disadvantages of storage devices including magnetic, optical and solid-state

Storage Devices and Media

Learning Objective

Know and understand the characteristics, uses, media types, advantages and disadvantages of the main storage technologies: magnetic, optical and solid‑state.

1. Magnetic Storage

1.1 Characteristics

• Data stored by magnetising tiny regions on a ferromagnetic surface.
• Read/write heads move over the surface (hard‑disk drives) or the media is spun (floppy disks, magnetic tapes).
• Typically uses rotating platters coated with a magnetic layer.
• Capacity measured in gigabytes (GB) to terabytes (TB).

1.2 Common Uses

• Primary storage in desktop and laptop computers.
• External backup drives.
• Archival storage on magnetic tape (e.g., LTO).

1.3 Media Types

• Hard‑disk drive (HDD) – sealed metal or plastic enclosure.
• Floppy disk – flexible magnetic disk in a protective jacket (now obsolete).
• Magnetic tape – long, thin strip wound on reels or cartridges.

1.4 Advantages

• High capacity at relatively low cost per gigabyte.
• Well‑established technology; widely compatible.
• Can be rewritable many thousands of times.

1.5 Disadvantages

• Mechanical parts are vulnerable to shock and wear.
• Slower access times compared with solid‑state media.
• Power consumption is higher than for SSDs.

2. Optical Storage

2.1 Characteristics

• Data recorded as pits and lands on a reflective surface.
• Read by a laser beam that detects changes in reflected light.
• Typically non‑volatile; data remains without power.
• Common formats: CD, D \cdot D, Blu‑ray.

2.2 Common Uses

• Software distribution and media (music, movies).
• Long‑term archival storage (e.g., master copies).
• Portable data exchange.

2.3 Media Types

• CD‑ROM / CD‑R / CD‑RW (up to 700 MB).
• D \cdot D‑ROM / D \cdot D‑R / D \cdot D‑RW / D \cdot D‑RDL (4.7 GB‑8.5 GB).
• Blu‑ray Disc (25 GB‑50 GB per layer).

2.4 Advantages

• Durable against magnetic fields.
• Relatively inexpensive for moderate capacities.
• Easy to distribute and read on many devices.

2.5 Disadvantages

• Limited capacity compared with modern HDDs/SSDs.
• Write speed is slower; many discs are read‑only.
• Susceptible to scratches, dust and laser degradation.

3. Solid‑State Storage

3.1 Characteristics

• Data stored in NAND flash memory cells; no moving parts.
• Access times measured in microseconds, far faster than magnetic media.
• Available as internal drives (SSD) or removable cards (SD, USB flash).
• Capacity ranges from a few gigabytes to several terabytes.

3.2 Common Uses

• Primary storage in laptops, tablets and high‑performance desktops.
• External portable drives for fast data transfer.
• Embedded storage in smartphones, cameras and IoT devices.

3.3 Media Types

• 2.5‑inch SATA SSD.
• M.2 N \cdot Me SSD (PCIe interface).
• USB flash drives.
• Secure Digital (SD) and micro‑SD cards.

3.4 Advantages

• Very fast read/write speeds; low latency.
• Robust – no mechanical wear, resistant to shock.
• Low power consumption, beneficial for battery‑operated devices.

3.5 Disadvantages

• Higher cost per gigabyte than magnetic storage.
• Limited write‑endurance (finite program/erase cycles).
• Data recovery after failure is more complex.

4. Comparison of Storage Technologies

5. Summary Checklist

1. Identify the physical principle used to store data (magnetism, light reflection, electrical charge).
2. Match each storage type with typical capacities and common applications.
3. Recall at least two advantages and two disadvantages for each technology.
4. Use the comparison table to decide which storage medium is most suitable for a given scenario (e.g., high speed vs. low cost).