Secondary Storage

Secondary Storage devices are used for long term storage of data.

All secondary storage devices are non-volatile, which means that they don't require power to continue to store data. They typically store significantly more data than primary memory, but are much slower for reading / writing data.

All secondary storage devices can be categorized into one of three classes, each has their own advantages and disadvantages:

Optical

Factor

Details

How it works

Laser burns pits into a layer of dye on the surface of a disk. The laser reflects from the areas where there are no pits, land, (1s) and will not from where there are pits (0s)

Capacity

Low

Read/Write speed

Slow (especially during random read)

Portability

Portable, but can be scratched

Examples

CD, DVD, BluRay

Magnetic

Factor

Details

How it works

The disk is covered in a substance that can be magnetised. A magnetic head writes 1s and 0s to the surface using ‘North” and “South”

Capacity

Highest

Read/Write speed

Medium speed

Data can be read / write in a random way (HDD)

Portability

Can be portable, but are comparatively large, can be damaged easily

Examples

Hard Disk Drive, MagneticTape

Solid State / Flash

Factor

Details

How it works

Uses NAND transistors, traps electrical currents into “pools”. A full pool is a 1, an empty pool is 0

Capacity

Medium (high £ per GiB, but maximum capacity can be high)

Read/Write speed

Fastest

Portability

Can be small / portable, Fast data storage, Durable

Examples

SSD, USB Flash Drive, Build in Flash Storage, SD Card

 


Included in the following specifications:
Edexcel GCSE Computer Science
OCR GCSE Computer Science