topic 3: storage devices and media

magnetic tape

thin strip of plastic coated in magnetic layer, used in applications where batch processing is used, as well as back up media and long term archives

advantages of magnetic tapes

generally less expensive, robust, huge data capacity

disadvantages of magnetic tapes

very slow data access times, very slow updating of data, affected by magnetic field (data can be corrupted)

HDD

data stored digitally on the surface of hard disks, used for storing OS and storing applications software

actuators

used to move read/write heads

read/write arm

swings the read/write head back and forth across the platter

read/write head

contains a tiny magnet which allows the data on the platter to be read

tracks

where the data is stored on the HDD, and each track is broken up into sectors

file allocation table

map of sectors so when new data is added, it can find the empty sector

advantages of HDD

have fast data transfer rate, fast access times, large memory capacities

disadvantages of HDD

easily damaged, many moving parts, quite noisy during read/write operation

pits and lands

how data is stored on a spiral track on optical media

CD/DVD - R

write only once, used for home recording of musics and films, to stored data for later use

advantages of CD/DVD - R

cheaper than RW disks, behave like a ROM when burnt

disadvantages of CD/DVD - R

can only be recorded once, not all CD/DVD players can read it

CD/DVD - RW

can read and write multiple times, used to record TV programmes, CCTV systems and backup devices

advantages of CD/DVD - RW

can be written many times, can use different file formats, not wasteful

disadvantages of CD/DVD - RW

expensive, and possible to overwrite data

CD/DVD - ROM

read only, used to store music files, software, computer games

advantages of CD/DVD - ROM

less expensive than HDD systems

disadvantages of CD/DVD - ROM

data transfer rate/data access times slower than HDD

advantages of blu-ray

can store more data than DVDs, automatically come with secure encryption system, ability to skip to any part of the disc, fast transfer rate, large storage capacity

disadvantages of blu ray

relatively expensive discs, encryption problems, DVD players introduced

SSDs

used like an HDD but has no latency issues

Advantages of SSD

More reliable, lighter, low power consumption

Disadvantages of SSD

shorter longevity (amount of data that can be operated in a few years is low)

Pen drives

Use SSD but are portable and connect through a USB port

Advantages of pen drive

Compact and portable, robust, no need for additional software to work

Disadvantages of pen drive

Easy to lose, careful on removing the USB

Memory cards

A card that can be inserted into a device which can read the card or allow data to be written to the card

Advantages of memory card

Very compact, very durable, can hold lots of data

Disadvantages of memory cards

Lower storage capacity compared to HDD, expensive per gb, have a finite life