The uses of magnetic, flash and optical storage devices

1.1.3 Input, output and storage

Input, output and storage — Note 2 of 4

Candidates need to understand that there are different types of storage device. They need to know about the characteristics of each type (magnetic, optical and flash) and understand the benefits and drawbacks of each, and be able to recommend an appropriate type of device for a given situation and justify the choice.

What you need to know

Secondary storage devices are magnetic, flash (solid-state) or optical. Each type has different characteristics, so you must be able to compare them and recommend the most suitable type for a situation.

What to know

Characteristics to compare: capacity, speed, portability, durability, reliability and cost.

Key terms

Magnetic storage: Data is stored as magnetised regions on a spinning platter (HDD) or tape, read and written by a moving head.
large capacity and low cost per GB, but slower and vulnerable to knocks because of moving parts. Tape is still used for large-scale archive backups.
Flash storage: Data is stored by trapping electrical charge in memory cells with no moving parts (SSD, USB stick, memory card).
very fast access, robust, silent, low power and portable, but more expensive per GB and has a limited number of write cycles.
Optical storage: Data is stored as pits and lands on a disc, read by a laser (CD, DVD, Blu-ray).
cheap to produce and easy to distribute, but low capacity, slow and easily scratched.

Exam technique

Tip:Match the characteristic to the need: a laptop needs durability and speed (flash); a server storing large media archives needs capacity at low cost (magnetic).
Mistake:Saying cost is 'cheap' without saying cheap per GB, or confusing the cost of the device with the cost per unit of storage.