| 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 |
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.
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).