Storage Devices Flashcards
Backing up data - what is it?
Backing up refers to the copying of files and data to a different medium in case of a problem with the main storage device
Backing up files and data on a regular basis is seen as good computing practice and many computer systems can be set to back up files automatically on a regular basis
The backups are often stored in a different place to the main storage
This is in case of fire or some other situation which could lead to irretrievable loss of key data and files
Why back up data?
Data could be lost due to failure of the original storage device, hardware failure
Hackers may corrupt or even cause you to lose the data completely
Viruses: usually caused by hackers to delete and destroy your data in a storage device
Might need backup if files need to be used elsewhere – original files are then protected against possible corruption or loss
However, backups do not necessarily guard against the effect of a virus – the virus could attach itself to the files which could mean that the backups were also affected
The 3 types of storage media?
Magnetic
Optical
Solid state
Fixed Hard Disks: magnetic
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Advantages Very fast data transfer rate and fast access times to data Have very large memory capacities Disadvantages Can be easily damaged They lack portability
Portable Hard Disks: magnetic
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Advantages
Data access time and transfer rate is very fast
Large memory capacities
Can be used to transfer information between computers
Disadvantages
Can be easily damaged
Magnetic Tapes: mainly used for backing up large amounts of data on networks
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Advantages Generally less expensive and very robust technology Data transfer rate is fast Disadvantages Access time is very slow When updating another tape is needed
CD-ROM and DVD-ROM: Optical
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Advantages Holds more data than floppy disks Less expensive than hard disk drives Disadvantages Data transfer rate and data access time are slower
CD-R and DVD-R: Optical
They are used for home recording of music (CD-Rs) and films (DVD-Rs)
They are used to store data for later use
Used in applications where it is necessary to prevent the deletion or over-writing of important data.
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Advantages Cheaper than RW disks Once burned (and finalized) they are like ROM Disadvantages Can only be reordered once Not all CD/DVD players and can read CD-R
CD-RW and DVD-RW: Optical
‘RW’ means that these disks are re-writable media can be written over several times
Unlike CD-R/DVD-R they don’t become ROMs
The recording layer uses a special phase-changing metal alloy
The alloy can switch between crystalline and amorphous (non-crystalline) phases, thus changing its reflectivity to light, depending on the laser beam power
Spots are produced which can be read by a laser
System allows data to be written, erased and re-written many times
CD-RWs and DVD-RWs are used to record radio and television programs
They are used in closed circuit television (CCTV) systems
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Advantages
Can be re used many times
Different file formats can be used each time
Less wasteful than R format since files or data can be added at a later stage
Disadvantages
Relatively expensive media
Possible to accidentally overwrite
DVD-RAM: Optical
Recent addition to optical media group
Unlike other CD and DVD formats, DVD-RAMs have several discrete concentric tracks rather than a single spiral track
Gives them advantage that writing and reading can occur at the same time
Makes it possible to watch an already recorded television program at the same time as a different program is being recorded
DVD-RAMs are used in recording devices such as satellite receivers to allow simultaneous recording
and playback
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Advantages
Have a long life (30 years)
Can be re written on more than the DVD-RWs (100,000 times)
Very reliable as they have built in verification software to ensure accuracy of data
Access is very fast
Very large capacities
Ability to read and write data at the same time
Disadvantage
DVD-RAMS are not as compatible as R or RW, many systems will not recognize this format
More expensive than DVD-RW
Blu-ray disks: Optical
Blu-ray disks are used in home video consoles
Used for storing and playing back films
PCs can use this technology for data storage or backing up hard drives
Camcorders can use this media to store film footage
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Advantage
Very large storage capacity
Data transfer rate is very fast
Data access speed is faster than with other optical media
Disadvantage
Disks are relatively expensive
Blu-ray disks still have encryption problems
Solid state storage devices - what are they
Solid state systems control the movement of electrons within a microchip: if the transistor conducts a current, this is equivalent to a 1, otherwise it is a 0
Have no moving parts, consume much less power and are extremely robust
Used primarily as removable storage devices and are collectively known as flash memory
Memory sticks/pen drives: solid state
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Advantage
Very compact and portable media
Very robust
Disadvantage
Not possible to write protect the data and files
Small physical size and are easy to lose.
Flash memory cards Used to store photos on digital cameras Mobile phones use them as memory cards Used in MP3 players to store music Used as a backup in hand held devices
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Advantages
Very compact
Very robust
Disadvantages
Very expensive per Gb of memory when compared to hard drive disks
Has a finite life in terms of the number of times they can be read from or written to
Lower storage capacity than hard disk
