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STORAGE

DEVICESAN 2015

+Storage Devices vs Storage Media

A storage device

is something that has the ability to read and write information

to and from a storage media

Eg. CD/DVD writer

Storage media

The components that store the information

Eg CD/DVDs, Hard disks, etc

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Computer memory is any physical device

capable of storing information temporarily or

permanently.

All computers have memory that is used to

hold the program instructions that the CPU

executes. The CPU can also write to and

store information in the memory.

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Memory

Primary

RAM ROM

Secondary

Hard Disk CD DVD

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Memory

PRIMARY SECONDARY

RAM ROM

To store data permanently

• Hard Disk

• CD

• DVD

Aka ‘backing storage’

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Primary Memory

RAM ROM

is a Volatile memory

is temporary memory

is memory that loses its

contents when the computer is

turned off

the more RAM a system has –

the faster it will run

is Non-volatile memory

is permanent memory

is memory that keeps its

contents even if the power is

lost

usually used to store the

essential program drivers to

start the computer

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+Backing storage

Any type of data storage device apart from RAM or ROM

Used to store data permanently even when the computer is

turned off

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+How Computer Memory Is Measured

Bit

All streams of input symbols to a digital system are evolved with 2

distinct symbols. These symbols are 0 (zero) and 1 (one), and are known

as Binary Digits or Bits.

Byte

A byte consists of eight bits

Kilobyte

A kilobyte (KB) consists of 1024 bytes

Megabyte

A megabyte (MB) consists of 1024 kilobytes

Gigabyte

A gigabyte (GB) consists of 1024 megabytes

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+Secondary Storage Devices

[also known as . . .

. . . external memory and auxiliary storage]

Secondary storage is a storage

medium that holds information

permanently until it is deleted or

overwritten even when the computer is

turned off

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+Memory Terms

Main or Internal memory

RAM & ROM

Backing storage

Any other memory other than RAM & ROM

Serial or Sequential Access

Data is stored in a sequential sequence so that information stored canonly be accessed by scanning through the data to that point. Eg. Tapes

Direct or Random Access

Any piece of information stored on a random access device can beaccessed without having to scan through its whole contents. Muchfaster than serial access. Eg. CD, DVD

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+Backing Up – Backup Models

Unstructured Backup

Selecting files

Full System Backup

Incremental Backup

Backups after Full System Backup

Off-site Backup

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+Backup Solutions

Manually copying

Software backup

Mirroring (RAID)

Two or more hard discs are linked such that information is written to

both of them at the same time, creating clones

Online or Remote backup

Files backed up via the internet to an online server usually by a third

party software installed on computer. Cloud computing !

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+

Thank You

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