1. 3.1 Storage devices and media
Revision

2. Think about what we store on our computers
3.1 Storage devices and media
What is data Storage
Storage means putting data into a known place so we can come back to it
We say that we can:
Write Data (saving)
Read Data (opening)
Think about what we store on our computers

3. Main Memory Vs Backing Storage
3.1 Storage devices and media
Main Memory Vs Backing Storage
Main Memory
Backing Storage
Sometimes known as Internal Memory or primary memory
Backing storage some known as secondary storage
Includes RAM and ROM
Name for all other storage devices as part of a computer like hard drive
Usually used to store data temporarily (in the case of RAM)
Usually used to store data over a long time
Usually used to store data while it is being processed by the CPU
Usually used to store application software, operating system software, files etc
Is volatile – means data will be lost if computer is turned off
Non-volatile - Means data will not be lost of computer is turned off.

4. Storage device – reads the data from the storage medium
3.1 Storage devices and media
Storage Media & Devices
Storage medium is the name given to the device that actually holds the data
Storage device – reads the data from the storage medium
Sometimes the storage medium is fixed (permanent) i.e. magnetic coated disks build into hard drive
Sometimes the storage medium is removable from the device i.e. CD ROM that can be taken out of the drive

5. Serial/Sequential Access
3.1 Storage devices and media
Serial/Sequential Access
Serial (sequential Access)
Direct (Random Access)
Files are stored one by one in a sequence
Stores files so that they can instantly be accessed
Must search through the files one by one until you get to the one you want
No need to search through files to get to the one you want
Example: VHS tape, Cassette Tape, Magnetic Tape
Example: DVD, CD ROM, Blu-ray, external hard drive, flash drive
Remember:
Serial: With a cassette you have to fast forward to get to a specific point.
Direct: You can skip to a particular scene with a DVD.

6. Increase in storage capacity
3.1 Storage devices and media
Data Storage Capacity
Data storage devices are have very different capacities. Some Can store large amounts of data while others can store lots:
Floppy Disk 1.4MB
CD-ROM
700MB
DVD
4.7GB
Blu-Ray
25 GB – 128GB
Hard Drive
8 TB
Increase in storage capacity
Magnetic Tape
Up to 185 TB 

7. 3.1 Storage devices and media
Magnetic Storage Devices
Magnetic storage media and devices store data in the form of tiny magnetised dots.
These dots are created, read and erased using magnetic fields created by very tiny electromagnets.
In the case of magnetic tape the dots are arranged along the length of a long plastic strip which has been coated with a magnetisable layer (audio and video tapes use a similar technology).

8. Storage Access Speeds Portability Access Type Durability Use
3.1 Storage devices and media
Magnetic Storage - Hard Drives: fixed and Portable
Storage
Very large capacity – even up to several terabits
Access Speeds
Random Access - so very fast access speeds
Portability
Fixed Hard drive – not portable
Portable Hard Drive – can move data from one computer to another
Access Type
Random (Direct) access
Durability
Fixed – less likely to break as fewer accidents can occur
Portable – more likely to break being carried out
Use
Fixed – is the main backing storage device used by all computers

9. Storage Access Speeds Portability Access Type Durability Use
3.1 Storage devices and media
Magnetic Storage: Magnetic Tape
Storage
Very large capacity – more than magnetic hard drives
Access Speeds
Serial Access – so slow compared with magnetic hard drives
Portability
Backed up magnetic tapes are normally stored away in a fire proof safe
Access Type
Serial Access
Durability
Quite durable as normally kept in a safe place
Use
Usually used to back up data stored on networks
Normally cheaper to store data per bite compared with magnetic disks

10. Magnetic tape uses 'serial access' to find a piece of data.
3.1 Storage devices and media
Magnetic Storage: Magnetic Tape
Many organization's, such as your school or an office, need to back up large volumes of data each day.
Large organizations who need to back up their systems daily tend to use magnetic tapes to store their data.
Magnetic tape uses 'serial access' to find a piece of data.
This means that to find a specific piece of data, the tape reader has to start at the beginning of the tape and continue fast forwarding until it gets to the piece of data that needed.

11. A Laser beam is the usual light source.
3.1 Storage devices and media
Optical Media
Optical storage devices are devices that save data as patterns or dots.
A Laser beam is the usual light source.
Data is read by bouncing the laser beam off the surface off the medium.
A Laser can also be used to write (make dots) which is otherwise known as burning.

12. Name CD ROM DVD ROM Blu-Ray Storage Access Type Use
3.1 Storage devices and media
Optical Media
Name
CD ROM
DVD ROM
Blu-Ray
Storage
700MB
4.7GB
20-128GB
Access Type
Random Access
Use
Audio CDs
Low quality movies
Small Applications/games
High quality movie
Software
Games
High-definition video (1080p)
High-definition audio
Stereoscopic 3D
PlayStation 3 games
PlayStation 4 games
Xbox One games

13. CD-R and DVD-R You can write to the CD/DVD but not erase anything
3.1 Storage devices and media
Optical Media - R – Read and W-Write
CD-R and DVD-R
You can write to the CD/DVD but not erase anything
Use the CD/DVD until they become full
CD-RW and DVD-RW
You can read and write to the CD/DVD – add and delete data as often as you like
DVD RAM
Very reliable and used to store movies for a long time
Used in many camcorders and comes with a special protective case

14. The term ‘solid-state’ essentially means ‘no moving parts’.
3.1 Storage devices and media
Solid ‘state’
The term ‘solid-state’ essentially means ‘no moving parts’. 
Solid-state storage devices are based on electronic circuits with no moving parts (no reels of tape, no spinning discs, no laser beams, etc.)
Solid-state storage devices store data using a special type of memory called flash memory...

15. Device Access Type Capacity Use Notes Solid ‘state’
3.1 Storage devices and media
Solid ‘state’
Device
USB Memory stick
Memory Card
Smart Card
Access Type
RANDOM
Capacity
Up to 128GB
64GB
Small but more that magnetic strip
Use
Used to store computer files
Used in phones a cameras
Used Satellite TV cards, and modern credit cards at Chip-and-pin terminals
Notes
More robust (strong) that memory and smart cards
Easily lost and easily broken

16. You could delete a file by accident Your computer could break down
3.1 Storage devices and media
Backups
Backup means making one or more copies of your data in case you lose your data?
Why?
You could delete a file by accident
Your computer could break down
Your computer could get infected by a virus which could edit data
Your laptop is stolen or becomes damaged
Most businesses use computers to store very important data (customer records, financial information, designs for products, etc.) If this data is lost, the business could possibly have to close. Backing-up business data is essential.

17. Personal backups of the data on your hard-drive can be made by…
3.1 Storage devices and media
How are Backups created
Personal backups of the data on your hard-drive can be made by…
Burning files to a CD-R
Copying files to an external hard-drive
Copying the files to another computer on a network
Business backup data by:
Making copies of data very regularly
Using large-capacity media such as magnetic tape
Keeping old copies of backups, just in case
Automating the system so that nobody forgets to do it!
Keeping backup media off-site (in case of fire or theft)