1. HDD vs SSD
Key Revision Points

2. HDD
In these devices the binary data is stored on the magnetised surface in a circular pattern on the surface of flat, circular plates called platters. These rotate at very high speed and a read/write head moves from side to side to load and save data.

3. Comparing Storage
When comparing any storage media (not just HDD and SSD) you should compare:
Capacity
Speed
Portability
Durability
Reliability

4. HDD Advantages Relatively cheap in terms of capacity per unit price.
Very reliable, lasting for many years in typical use.
Very large capacity, significantly larger than any other form of secondary storage.

5. HDD Disadvantages
Vulnerable to damage if moved too violently, particularly while reading/writing data which can damage the read/write head
Slower read/write times than SSDs

6. They form the main storage for Smartphones
SSD
Solid state devices are a form of flash memory, it is therefore non-volatile like ROM so the contents are not lost when there is no power supply, but able to be written to as in RAM.
Solid State Devices can replace the hard drive as the main secondary storage device in a computer, where really large storage capacities are not required. 
They form the main storage for Smartphones

7. They don’t need defragmenting
SSD Advantages
Solid State Devices offer faster read/write times than either magnetic or optical storage devices.
They are also silent and resistant to physical shock which makes them ideal as portable storage devices.
They don’t need defragmenting

8. SSD Disadvantages
The storage capacity cannot yet match that of modern hard drives.
Relatively expensive compared to magnetic media in terms of data capacity per unit price so they tend to be smaller capacity than magnetic storage devices.
They can only be written to a limited number of times

9. Textbook and Firefly
Textbook pages 6-7