2.2: Secondary Storage

Exam Board:
OCR

Specification:
2020

Secondary storage is non-volatile storage used to save and store data that can be accessed repeatedly.

Secondary storage is not directly embedded on the motherboard (and possibly even external) and therefore further away from the CPU so it is slower to access then primary storage

Storage Characteristics you should know: 

CAPACITY: The maximum amount of data that can be stored on the device.

 
DURABILITY: The strength of the device, to last without breaking.

 

PORTABILITY: How easy it is to carry the device around.

 

ACCESS SPEED: How quickly data on the device can be read or edited.

 

COST: The average price it costs to purchase a storage device.

RELIABILITY: The likelihood of the device continuing to perform well over time.

Magnetic Storage

A magnetic hard disk drive (HDD) is the most common form of secondary storage within desktop computers. A read/write head moves nanometres above the disk platter and uses the magnetic field of the platter to read or edit data.

 

An obsolete (no longer used) type of magnetic storage is a floppy disk but these have been replaced by solid state devices such as USB sticks which are much faster and have a much higher capacity. 

 

Another type of magnetic storage that is still used is magnetic tape. Magnetic tape has a high storage capacity but data has to be accessed in order (serial access) so it is generally only used by companies to back up or archive large amounts of data.

Magnetic Storage Characteristics: 

- Large CAPACITY and cheaper COST per gigabyte than solid state.

X - Not DURABLE and not very PORTABLE when powered on because moving it can damage the device.

X - Slow ACCESS SPEED but faster than optical storage.

Optical Storage

Optical storage uses a laser to project beams of light onto a spinning disc, allowing it to read data from a CD, DVD or Blu-Ray

This makes optical storage the slowest of the four types of secondary storage.

Disc drives are traditionally internal but external disc drives can be bought for devices like laptops.

Magnetic Disks are spelled with a k and Optical Discs have a c.

Optical Storage Characteristics: 

X Low CAPACITY: 700 MB (CD), 4.7 GB (DVD), 25 GB (Blu-ray).


X - Not DURABLE because discs are very fragile and can break or scratch easily.


 Discs are thin and very PORTABLE. Also very cheap to buy in bulk.

X Optical discs have the Slowest ACCESS SPEED.

Solid State Storage

There are no moving parts in solid state storage.

 

SSDs (Solid State Drives) are replacing magnetic HDDs (Hard DIsk Drives) in modern computers and video game consoles because they are generally quieter, faster and use less power.  

A USB flash drive (USB stick) is another type of solid state storage that is used to transport files easily because of its small size.

Memory cards, like the SD card in a digital camera or a Micro SD card in a smartphone, are another example of solid state storage.

Solid State Characteristics: 

X High CAPACITY but more expensive COST per gigabyte than magnetic.

Usually DURABLE but cheap USB sticks can snap or break

The small size of USB sticks and memory cards mean they are very PORTABLE and can fit easily in a bag or pocket.

Solid State storage has the fastest ACCESS SPEED because they contain no moving parts.

Questo's Questions

2.2 - Secondary Storage:

1. Rank magnetic, optical and solid-state storage in terms of capacity, durability, portabilityspeed and cost. For example, magnetic has the highest capacity, then solid-state, then optical. This could be completed in a table. [15]

2. Justify which secondary storage should be used in each scenario and why it is the most appropriate:

  • a. Sending videos and pictures to family in Australia through the post. [2]

  • b. Storing a presentation to take into school. [2]

  • c. Storing project files with other members of a group to work on together. [2]

  • d. Backing up an old computer with thousands of files to a storage device. [2]