HDD vs SSD
The storage race
Your mission
Your friend's laptop takes forever to open files, and they want to know why. Look inside both kinds of storage drive, race them head to head, then help your classmates choose the right drive for each job.
Explore
Tap each + to find out what is inside a hard disk drive and a solid-state drive.
Both drives store your files when the computer is switched off, but they work in completely different ways. Tap each + to look inside.
0 of 7 parts explored
Experiment
Choose a file and settings, then open it on both drives at the same time. Run at least two races with different settings to continue.
Waiting to start.
Waiting to start.
0 of 2 races run
Challenge
Eight people need a new drive. Choose HDD or SSD for each, then finish with one last puzzle.
Solve all 9 to continue.
Understand
Here is what the race was showing you, in the words you need for the exam.
HDD vs SSD at a glance
| HDD | SSD | |
|---|---|---|
| How data is stored | Magnetic patterns on spinning disks (platters) | Electrically, in flash memory chips |
| Moving parts | Yes: spinning platters and a moving read/write head | None |
| Speed | Slower: the head must move and the disk must spin round | Faster: data is read electronically |
| Bumps and drops | More easily damaged | More resistant to shocks |
| Noise and power | Can be noisy, uses more power | Silent, uses less power |
| Cost per gigabyte | Lower | Higher |
| Good for | Large, cheap storage: archives and backups | Laptops, phones, fast start-up and apps |
Why the HDD keeps you waiting
To read data, an HDD must do three things in order:
- Move the head to the correct track, a circular path on the disk.
- Wait for the right sector (a piece of the track) to spin round under the head.
- Read the magnetic pattern.
Moving the head and waiting for the disk to spin both take time. That's why a scattered file was so much slower.
Both are secondary storage
HDDs and SSDs are both non-volatile: they keep your files when the power is off. That's different from RAM, which is volatile and loses everything without power.
When you open a program, it is copied from storage into RAM so the CPU can run it. So a fast SSD doesn't replace RAM: the computer needs both.
Words to know
- Platter
- A spinning disk inside an HDD, coated with magnetic material.
- Read/write head
- Moves across the platter to read and write the magnetic patterns.
- Track
- A circular path on the disk surface.
- Sector
- A subdivision of a track.
- Flash memory
- Chips that store data electrically, with no moving parts. Used in SSDs and USB drives.
- Non-volatile
- Keeps its data when the power is switched off.
Exam tip
When a question asks you to choose a drive, match it to what matters most, and always give a reason. Speed, shock resistance and low power point to an SSD. Lots of capacity at a low cost per gigabyte points to an HDD.