Lesson 5. Storage

Lesson Objective

Explain how Magnetic, Solid State and Optical Storage funtions.
State the advantages and disadvantages of Magnetic, Solid State and Optical Storage.
Know what cloud storage is and name some advantages and disadvantages.
Understand the factors that affect the choice of storage devices.

Lesson Notes

Storage Devices

Refers to any hardware component that stores data long term. Data on storage devices are not lost when the power is turned off.

The 3 main types of storage are:

Magnetic - Hard Disk Drives
Solid State - Solid State Drives, USB Flash Drives
Optical - CDs, DVDs, Blu-Ray

Magnetic Storage

A magnetic disk drive consists of a number of platters (disks) coated in a magnetic material. The data is encoded into bits and written onto the surface as a series of changes in the direction of the magnetisation. Data is stored in small areas on the disk called sectors. A "metal arm" is used to read and write to the disk.

HDD Advantages

Cheaper than Solid State
Higher capacity than Solid State
Longer read/write cycle than Solid State

Examples:

Solid State Storage

Solid-state storage (SSS) refers to a type of non-volatile computer storage that stores and retrieves digital information using only electronic circuits, without any involvement of moving mechanical parts.

Most solid-state storage devices use NAND flash memory, which is electrically programmable and non-volatile.

SSD Advantages

Faster than HDDs
Does not need to be defragmented
Shockproof
Makes basically no noise
Low power consumption

Examples:

Comparing Magnetic (HDD) and Solid State (SSD) Storage

Price: SSDs are about 10 times more expensive than HDDs per MB
Power: HDDs uses about 3 times more battery power than SSDs
Capacity: SSDs are generally no larger than 512 GB but HDDs go up to 4 TB
Speed: SSDs are almost twice as fast at loading up and copying files
Noise: SSDs are silent whereas HDDs make spinning disc sounds
Reliability: Both are highly reliable forms of storage but the magnetic disc is more vulnerable to knocks as it has moving parts

Optical Storage

Storage on disks. Data is read using a laser. Data is stored on small indentations (data pits) on the shiny surface of the disk.

Advantages:

Cheap
Portable

Disadvantages:

Low storage capacity
Easily damaged

Examples:

AQA Mark Scheme - How is works?

The tracking mechanism moves the laser into the correct position over the CD;
The CD is spun to ensure all data can be read;
The CD spins slower when the laser/read-head is above the outer tracks;
The laser is shone on to the disk;
The laser is reflected;
Bumps/pits are raised parts of the disk;
Bumps/pits form a spiral from the centre to the outside of the disk;
A (opto-electric) sensor detects changes in reflectivity;
Bumps/pits and lands represent the two possible bit values

Cloud Storage

The "Cloud" refers to software applications and data are held on a remote server on the Internet. It is typically accessed using a Web browser such as Chrome or Edge.

Examples:

Google Drive
One Drive
Dropbox
iCloud

Advantages of Cloud Storage:

Access files from any connected device.
Files can be shared easily.
Easy to increase storage.
Backing up data is no longer crucial, it is done by the service provider.
Service provider also provides security.
Can store data for free - Limit.
Does not require expensive hardware.

Disadvantages of Cloud Storage:

Need an Internet connection.
Upload/download speed depends on bandwidth.
Dependent on host for security and back-ups.
Data can be vulnerable to hackers.
Unclear who owns the cloud data.
Subscription fees may be expensive - Long term.

Factors that affect the choice of storage

Cost
Storage Size
Physical Size
Performance
Reliability

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Lesson 5. Storage

Lesson Objective

Lesson Notes

Storage Devices

Magnetic Storage

Solid State Storage

Comparing Magnetic (HDD) and Solid State (SSD) Storage

Optical Storage

AQA Mark Scheme - How is works?

Cloud Storage

Advantages of Cloud Storage:

Disadvantages of Cloud Storage:

Factors that affect the choice of storage

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