This comparison covers Complete Comparison: HDD vs SSD vs Optical within Secondary Storage for GCSE Computer Science. Revise Secondary Storage in 3.4 Computer Systems for GCSE Computer Science with 17 exam-style questions and 18 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 7 of 11 in this topic. Use this comparison to connect the idea to the wider topic before moving on to questions and flashcards.
Complete Comparison: HDD vs SSD vs Optical
| Aspect | HDD (Magnetic) | SSD (Solid State) | Optical (CD/DVD/BD) |
|---|---|---|---|
| Speed | Slow (100-200 MB/s) | Very fast (500-7000 MB/s) | Very slow (1-8 MB/s) |
| Capacity | High (1-20 TB) | Medium (256GB-4TB typical) | Low (700MB-100GB) |
| Cost per GB | Cheapest (£0.02-0.03) | Expensive (£0.10-0.15) | Cheap per disc but low capacity |
| Durability | Fragile - moving parts | Durable - no moving parts | Fragile - can scratch |
| Power Use | High (5-10W active) | Low (2-4W active) | Moderate (drive needs power) |
| Noise | Noisy (spinning, seeking) | Silent | Moderate (spinning) |
| Portability | Moderate (needs protection) | High (shock-resistant) | Very high (lightweight, no power) |
| Lifespan | 3-5 years typical | 5-10 years (limited writes) | 10-25 years if stored well |
| Best For | Bulk storage, backups | OS, apps, speed-critical tasks | Distribution, archives |
Which storage device? Scenario by scenario
Exam questions ask you to recommend AND justify — this is the reasoning that scores.
- A travelling salesperson's laptop, knocked about in a car bootSSD. No moving parts, so it survives being dropped or vibrated. An HDD's spinning platter and moving read/write head can be damaged by the same shock, causing data loss.
- A school archiving years of CCTV footage as cheaply as possibleHDD. Much lower cost per GB at very large capacities. Speed is not critical because the footage is only reviewed occasionally.
- Mass-distributing a game as a physical copyOptical disc. Very cheap to mass-produce once a master exists, portable, and needs no internet connection to install.
- A gaming PC where boot and level-load times matterSSD. Far faster read/write and access speeds — no read/write head has to physically move to the right spot on a spinning disk.
- A photographer storing thousands of RAW files on a budgetHDD. Largest capacity per pound, which suits bulk storage of large files where access speed matters less than affordable space.
- Council records that must never be alteredWrite-once optical disc. Once written the data physically cannot be changed, giving a tamper-proof record — unlike HDD/SSD where files can be overwritten.
Practice questions for Secondary Storage
Which of the following is a characteristic of secondary storage?
Describe how data is stored on a magnetic hard disk drive (HDD).