Chapter 3 - Storage devices and media

Describe serial / sequential access

- Files are stored one by one in a sequence. - Must search through the files one by one until you get to the one you want.

Describe direct / random access

- Stores files so that they can be instantly accessed - No need to search through the files to get to the one you want

Describe a DVD-RAM

- Used when data constantly needs to be re-written. - Can hold up to 10GB of data

Uses of a DVD-RAM

- commonly used in recording equipment

Why should we use backup storage?

- could delete a file by accident - computer could break down - computer could get infected by a virus, which could edit data - laptop could be stolen / damaged - data could be corrupted by hackers

Describe a CD-R / DVD-R

- only recordable once. - once the process has been finalised then the disks become Read Only.

Uses of a USB Memory Stick

- transfer files between computers - backup storage (work)

Uses of magnetic tapes

- used by large organisations to make daily backups of their networks - used for long-term archiving of data.

Uses of CD-RW and DVD-RW

- used in CCTV - record television programs

Main Memory VS Backing Storage

- used to store data temporarily ; store data over a long time - used to store data while it is being processed by the CPU ; used to store applications software, operating system software, files, etc. - volatile (data will be lost if the computer is turned off) ; non-volatile

What are CD-Rs / DVD-Rs used for?

1. Backup of data 2. Audio CDs

What are the ways personal backups can be created?

1. Burning files to a CD-R 2. Copying files to an external hard drive 3. Copying files to a USB 4. Copying files to another computer on a network

List examples of optical media

1. CD-ROM 2. DVD-ROM 3. Blu-Ray

Disadvantages of CD-RW and DVD-RW

1. Can be expensive. 2. Data could be overwritten.

Disadvantages of a USB Memory Stick

1. Easy to lose 2. Could be damaged if incorrectly ejected.

List examples of magnetic storage devices

1. Fixed Internal Hard Drive 2. Portable Hard Drive 3. Magnetic Tapes 4. Memory Cards

Advantages of a CD-ROM

1. Hold more data than floppy disks. 2. Cheaper than hard drives and USBs 3. Compatible with audio systems

Advantages of a Blu-Ray disk

1. Large storage capacity, used to store HD video content 2. Greater Access Speeds than other optical mediums 3. Secure Encryption System to minimise chances of copyright.

Advantages of a magnetic tape

1. Less expensive than the equivalent capacity on a hard disk drive. 2. Very robust, hard to break. 3. Huge storage capacity (compared to fixed and portable hard drives).

Advantages of a fixed internal hard drive

1. Less likely to break, as fixed 2. High storage capacities (compared to external drives) 3. Fast data transfer rate

Advantages of a DVD-RAM

1. Long life / more durable 2. Can be rewritten over 100000 times. 3. Very fast to access files. 4. Large storage capacity 5. You can read data at the same time it is being written.

3 main types of storage devices

1. Magnetic backing storage 2. Optical backing storage 3. Solid state backing storage

What are the ways business backups can be created?

1. Making copies of data regularly ( i.e. daily) 2. Using large capacity media (e.g. magnetic tape) 3. Keeping old copies of backups, just in case. 4. Automating the system - so no one forgets to do it. 5. Keeping backup media off-site, in case of fire or theft.

Disadvantages of a DVD-RAM

1. More expensive compared to other discs. 2. Don't work in as many devices as other discs. (Not compatible with all playback formats)

Disadvantages of a Blu-Ray disk

1. More expensive compared to other optical media. 2. Requires a separate player - more expensive. 3. Not all movie titles are available on Blu-Ray.

Disadvantages of a fixed internal hard drive

1. More moving parts (compared to solid state drives) 2. Incorrect shut down procedure could cause hard drive to malfunction.

Disadvantages of a portable hard drive

1. More prone to errors than a fixed hard drive. 2. Could be damaged if incorrectly ejected from the computer.

Disadvantages of CD-R and DVD-R

1. Not compatible with all players. 2. If disk has a burn error it cannot be used again.

Advantages of a portable hard drive

1. Portable 2. High storage capacity (compared to optical disks)

Advantages of a USB Memory Stick

1. Portable and small 2. Robust 3. Large storage capacity 4. No need for additional drivers / software

Types of access

1. Serial / Sequential access 2. Direct / Random access

Disadvantages of a CD-ROM

1. Slower data transfer rate compared to other storage medium. 2. Can be easily damaged / scratched

Disadvantages of a DVD-ROM

1. Slower data transfer rate compared to other storage mediums. 2. Have to buy a separate DVD player.

Disadvantages of a Memory Card

1. Smaller storage capacity 2. Quite expensive

Examples of solid-state storage devices

1. USB Memory Sticks 2. Memory cards

Advantages of a Memory Card

1. Very small, and can be removed and placed in other devices. 2. Robust

How is a Blu-Ray disk different from a CD-ROM and DVD-ROM?

Blu-Ray disks use a blue laser instead of a red laser used with CD/DVD ROMs.

Advantages of CD-RW and DVD-RW

Can be reused many times.

Advantages of CD-R and DVD-R

Cheaper than RW disks.

Examples of direct / random access

DVD, CD ROM, Blu-ray, external hard drive, flash drive

What type of access does a fixed internal hard drive use?

Direct / Random Access

What type of access does a portable hard drive use?

Direct / Random access

What type of access does a Blu-Ray disk use?

Direct / random access

What type of access does a USB / Memory Card use?

Direct / random access

Advantages of a DVD-ROM

Holds more data than CD-ROMs: - can store larger applications - videos are in higher resolutions

Uses of a fixed internal hard drive

It is the main backing storage device used by all computers to store: - operating systems and system files - applications - files (documents, images, videos, audio, et.c)

What type of storage device is a fixed internal hard drive?

Magnetic Storage device

What kind of storage device is a magnetic tape?

Magnetic storage device

What type of storage device is a portable hard drive?

Magnetic storage device

Difference between R and RW disks

R: Write once only RW: Can be written to or read from many times.

What type of access does a magnetic tape use?

Serial / sequential access

Uses of a Memory Card

Used to store files on: - digital cameras - mobile phones - MP3 players

Examples of serial / sequential access

VHS tape, Cassette tape, Magnetic tape

Disadvantages of a magnetic tape

Very slow data access - The tape reader must start at the beginning of the tape and continue fast-forwarding until it gets to the piece of data needed.

Describe CD-RW and DVD-RW

allows for data to be written, erased, and re-written many times.

Describe how solid-state storage devices work

based on electronic circuits with no moving parts. store data using a special type of memory called flash memory.

Uses of a portable hard drive

connects to the computer using the USB port. are used to store: - personal backup data - transfer files between computers / devices

What type of access does a CD-ROM use?

direct / random access

What type of access does a DVD-ROM use?

direct / random access

The role of secondary storage devices

ensures data is stored permanently so that it can be used again at a later date.

What is meant by the term 'backup'?

making one or more copies of your data in a different storage medium.

How does optical media/storage work?

save data as patterns or dots. Data is read by bouncing the laser beam off the surface of the medium.

How does magnetic storage media work?

stores data in the form of tiny magnetised dots. These dots are created, read, and erased using magnetic fields created by very tiny electromagnets.

Storage medium is the name given to ...

the device that actually holds the data.

Uses of a DVD-ROM

used to store: - DVD movies - software applications - computer games

Uses of a Blu-Ray disk

used to store: - HD Movies - Large software / Game applications - used in cartridge form in camcorders

Uses of a CD-ROM

used to store: - audio CDs - software applications - device drivers