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This lesson focuses on comparing different storage technologies in depth across the key criteria: capacity, speed, portability, durability, cost per GB and suitability for different uses. For the OCR H446 exam, you will often be asked to recommend storage for a given scenario and justify your choice.
| Criterion | What It Means |
|---|---|
| Capacity | How much data can the device store? |
| Speed | How fast can data be read from or written to the device? (includes access time and transfer rate) |
| Portability | How easy is it to carry or move the device? Consider physical size, weight and power requirements |
| Durability | How resistant is the device to physical damage, shock, heat, water? |
| Cost per GB | How much does each gigabyte of storage cost? Important for budget decisions |
| Reliability | How likely is the device to fail? What is its expected lifespan? |
| Technology | Typical Capacity Range | Notes |
|---|---|---|
| HDD | 500 GB - 20+ TB | Highest capacity per single device. Ideal for bulk storage |
| SSD | 120 GB - 8 TB (consumer) | Capacities increasing rapidly. Common sizes: 256 GB, 512 GB, 1 TB, 2 TB |
| CD | 700 MB | Fixed capacity per disc |
| DVD | 4.7 GB (single layer), 8.5 GB (dual layer) | Fixed capacity per disc |
| Blu-ray | 25 GB (single layer), 50 GB (dual layer), 128 GB (BDXL) | Fixed capacity per disc |
| USB flash drive | 2 GB - 2 TB | Convenient, small form factor |
| SD card | 2 GB - 1 TB | Common in cameras, phones, drones |
| Cloud | Virtually unlimited | Limited only by subscription plan and provider capacity |
| Technology | Sequential Read Speed | Random Access | Notes |
|---|---|---|---|
| HDD | 80-250 MB/s | Slow (seek time: 5-15 ms) | Mechanical latency from head movement and platter rotation |
| SSD (SATA) | 400-550 MB/s | Very fast (0.1 ms) | Limited by SATA interface (6 Gb/s) |
| SSD (NVMe) | 2,000-7,000+ MB/s | Extremely fast | Uses PCIe interface; much faster than SATA SSDs |
| CD | 1.2-7.8 MB/s | Slow | 1x-52x speed ratings |
| DVD | 11-22 MB/s | Slow | 8x-16x speed ratings |
| Blu-ray | 36-54 MB/s | Slow | 1x-12x speed ratings |
| USB flash drive | 5-400 MB/s | Moderate | Depends on USB version (2.0, 3.0, 3.1, 3.2) |
| Cloud | Depends on internet speed | Depends on internet speed | Typically 10-1000 Mb/s depending on connection |
| Technology | Size/Weight | Power Source | Portability Rating |
|---|---|---|---|
| HDD (3.5") | Large, heavy | Mains power | Low |
| HDD (2.5") | Medium | USB powered | Moderate |
| SSD (2.5") | Small, light | USB/SATA powered | High |
| SSD (M.2) | Tiny (stick of gum size) | Internal only | N/A (internal component) |
| Optical disc | Very thin, lightweight | Needs a drive to read | High (disc itself), Low (needs reader) |
| USB flash drive | Very small, very light | USB powered | Very high |
| SD card | Tiny | Slot powered | Very high |
| Cloud | No physical device needed | Internet required | Highest (any device, anywhere) |
| Technology | Moving Parts | Shock Resistance | Water Resistance | Lifespan |
|---|---|---|---|---|
| HDD | Yes (platters, heads) | Poor — impact can cause head crash | Poor | 3-5 years typical |
| SSD | No | Excellent | Good (sealed) | 5-10 years; limited by write endurance |
| Optical disc | No | Moderate (can shatter) | Poor (surface damage) | Decades if stored properly (pressed discs) |
| USB flash drive | No | Good | Moderate | 10+ years if not frequently written |
| SD card | No | Good | Moderate | 10+ years |
| Cloud | N/A (server-side) | N/A | N/A | Indefinite (provider-dependent) |
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