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:
|
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 |
|
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 |
|
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 |