3.1 Storage devices and mediaRevision

3.1 Storage devices and mediaWhat 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

3.1 Storage devices and mediaMain 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.

3.1 Storage devices and mediaStorage 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

3.1 Storage devices and mediaSerial/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.

3.1 Storage devices and mediaData 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-ROM700MB

DVD4.7GB

Blu-Ray25 GB – 128GB

Hard Drive8 TB

Magnetic TapeUp to 185 TB

Increase in storage capacity

3.1 Storage devices and mediaMagnetic 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).

3.1 Storage devices and mediaMagnetic 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 anotherAccess Type

Random (Direct) access

Durability Fixed – less likely to break as fewer accidents can occurPortable – more likely to break being carried out

Use Fixed – is the main backing storage device used by all computers

3.1 Storage devices and mediaMagnetic 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

3.1 Storage devices and mediaMagnetic 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.

3.1 Storage devices and mediaOptical 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.

3.1 Storage devices and mediaOptical Media

Name CD ROM DVD ROM Blu-Ray

Storage 700MB 4.7GB 20-128GBAccess Type Random Access Random Access 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

3.1 Storage devices and mediaOptical Media - R – Read and W-Write

CD-R and DVD-RYou can write to the CD/DVD but not erase anythingUse the CD/DVD until they become full

CD-RW and DVD-RWYou can read and write to the CD/DVD – add and delete data as often as you like

DVD RAMVery reliable and used to store movies for a long timeUsed in many camcorders and comes with a special protective case

3.1 Storage devices and mediaSolid ‘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...

3.1 Storage devices and mediaSolid ‘state’

Device USB Memory stick Memory Card Smart Card

Access Type RANDOM RANDOM 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

3.1 Storage devices and mediaBackups

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.

3.1 Storage devices and mediaHow are Backups created

Personal backups of the data on your hard-drive can be made by…

Burning files to a CD-RCopying files to an external hard-driveCopying the files to another computer on a network

Business backup data by:Making copies of data very regularlyUsing large-capacity media such as magnetic tapeKeeping old copies of backups, just in caseAutomating the system so that nobody forgets to do it!Keeping backup media off-site (in case of fire or theft)