Handout 4 & 5: storage devices and media Flashcards
how is 1 and 0 represented in magnetic storage ?
- the iron oxide coating is magnetized for one , and demagnetized for 0
what is the big advantage of magnetic storage devices ?
- is that the data is permanent unless it is written over again
what are the most common devices that uses magnetic properties ?
- hard disk drives (HDD)
- magnetic tapes
what are secondary storage devices ?
- they are devices that ensures that the data is stored permanently so it can be used again at a later date
what is a storage medium ?
- a storage medium is the name given to the device that actually holds that data
what do we store on a secondary storage device ?
- Images , videos , Documents , Music , Games , Software, etc.
what do we mean by a serial ( sequential access) access ?
- Files are stored one by one
- you have to go through the files one by one until you get to the one you want
- in other words , data can only be read in the same order that it was written
For example : VHS tapes , cassette tapes , magnetic tapes
what do we mean by direct ( Random ) access ?
- stores files so that they can be instantly accessed
- no need to go through the files to get to the one you want
Examples : DVD , CD-Rom , blue rays , External hard drives , flash drives
what is the use of Magnetic Tapes ?
- due to it’s serial access of data which has a very slow speed for accessing data , it makes the magnetic tape useless in real time or online applications , it is best suited for offline or batch processing , but due to their vast storage capacity , it is used for long term archiving or by large organisations that make daily backups of their network on magnetic tapes
what are the advantages of magnetic tapes ?
- they have huge amount of data storage capacity compared to portable or fixed hard drives
- they are stored away in a fire proof room
- they are robust
- they are in-expensive
- they have very fast rates of data transfer
what are the disadvantages of magnetic tapes ?
- they have very slow rates of data access due to their serial data access type
- when updating the tape another tape is needed to store the final version
- can be affected by magnetic fields
how does a magnetic tape store data ?
magnetic storage media devices store data in the form of tiny magnetised dots , these dots are created , removed , erased and read by an electromagnetic field which is created by very tiny electromagnets
compare between data transfer rate and data access time ?
- Data transfer rate is the rate at which data is sent from the storage device to a computer and vice versa
- Data access time is the time needed to locate a certain file that is stored on the storage device
what is the use of a fixed internal hard drive ?
- it is the main storage device used by all computers for storing :
- applications
- files
- operating system and system files - it is also used in real-time system ( robots , controlling a chemical plant ) and in online-systems ( booking an airline ticket , automatic stock control )
- it is used in file servers for computer networks
what are the advantages of fixed internal hard drive ?
- they are less likely to break as they are fixed
- they have high storage capacity compared to portable hard drives
- they have fast data transfer rates and fast data access time
what are the disadvantages of fixed HDD ?
- they have more moving parts than SDD
- incorrect shut down procedure can malfunction the hard drive , which means it is easily to damage
- they are more noisy when compared to SDD
what is the use of portable HDD ?
- this device connects to the computer using one of the USB ports , it is used for :
- personal data backup
- transferring files from one computer to the other
what are the advantages of portable HDD ?
- portable , transferring files between devices
- high storage capacities compared to optical disks
- fast transfer rate of data and fast data access time ( not as fast as fixed HDD )
what are the disadvantages of portable HDD ?
- they are more error prone
- can be damaged if ejected incorrectly or dropped
- transfer rates of data and data access times are slower than fixed HDD
what is the use of a CD-ROM ?
- a CD-ROM is a read only disk , and they are normally used to store :
- audio CD’s
- Software applications
- Device drivers
what are the advantages of CD-ROM ?
- they have higher storage capacity than floppy disk
- they are cheaper than HDD or UBS’s
- they are compatible with audio systems
what are the disadvantages of CD-ROM ?
- they have slower data transfer rates than other sotrage mediums
- they are not robust , easily scrateched and damaged
how does an optical disk store and read data ?
- optical disks stores data as patterns or dots , then this data is read written by a laser beam bouncing off the surface of the medium
what are the uses of DVD-ROM ?
- DVD-ROMS are read only , they are used to store :
- DVD movies
- software applications
- computer games
what are the advantages of DVD-ROMS ?
- can hold more data than CD-ROMS
- can store larger application
- videos is higher resolution
what are the disadvantages of DVD-ROM ?
- data transfer is slower than other storage mediums
- have to buy a separate DVD player
what are the uses of Blu-Ray disks ?
- they use a blue laser rather than red laser used with CD/DVD ROMS , Blu-Ray disks are normally used to store :
- HD movies
- Larger software / games applications
- In camcorders in cartridge form
what are the advantages of Blu-Ray disks ?
- large storage capacity used to store HD video content
- data access time is faster than other optical medium devices
- fast data transfer rates
- secure encryption system to minimise chance of copyright
what are the disadvantages of Blu-Ray disks ?
- they more more expensive compared to other optical storage devices
- there is the need of buying a separate player
- not all movie titles are available on blu -ray dikss
what are CD-R and DVD-R ?
CD-R and DVD-R can be used once , once they have been used and finalised they will become read-only
what are some of the uses of CD-R and DVD-R ?
- backup data
- audio CDs
what are the advantages of CD-R and DVD-R ?
- cheaper than CD-RW
- once burned and finalised they behave like a ROM
what are the disadvantages of CD-R and DVD-R ?
- not compatible with all players
- if an error has occurred with the burning of the CD or DVD then it can not be used again
what are CD-RW and DVD-RW ?
- they allow for the data to be written , erased and rewritten many times
what are some of the uses of CD-RW and DVD-RW ?
- in CCTV
- and when recording television programms
what are the advantages of CD-RW and DVD-RW ?
- they can be reused many times
- Data can be added at a later stage
what are the disadvantages of CD-RW and DVD-RW ?
- more expensive
- data can be overwritten
what are DVD RAM ?
- they are used when data needs to be rewritten constantly. DVD RAM can hold up to 10 GB of data and commonly used in recording equipment
what are the advantages of DVD RAM ?
- long life
- large capacity
- can be rewritten many times
what are the disadvantages of DVD RAM ?
- can be expensive
- not compatible with all playback formats
what are SSD ?
- they have rapidly taken over from HDD as the main storage device , as the name suggests they use solid-state media and can be used in the same way as an HDD so it can store :
- files
- application software
- operating system
what are the advantages of SSD compared to HDD ?
- more reliable
- they are thinner
- they have no moving parts
- they run much cooler than HDD
- they do not have to get to speed to start working properly
- they have fast data transfer rates
- and faster data access time
- ## have lower power consumption
what are the disadvantage of SSD ?
- there longevity of this technology and the durabilty of it
what are solid state devices ?
they are based on an electric circuit and have no moving parts they store data and used a special type of memory called flash memory
uses of USB memory stick ?
- they connect to the computer via a USB port . And they are used to backup and transfer files between computers , and is used as a security device to prevent software piracy
what are the advantages of a USB memory stick ?
- they are robust
- they are light
- they are not affected by magnetic fields
- they have large storage capacities
- they do not need an additional software / device drivers
what are the disadvantages of USB memory stick ?
- they can not be made as read only
- easy to loose
- can be damaged if not ejected properly
what are memory cards used for ?
- they are used to store files on digital cameras , mobile phones and mp3 players and used as a backup device for hand-held devices
what are the advantages of memory cards ?
- they are small and can be transferred into another device easily
- robust
- can store large amounts of data
what are the disadvantages of memory cards ?
- they are quite expensive
- small capacites comapred to other storage devices
- they need special reader / player
what is backup ?
- backup means making one or more copies of your data in different storage mediums
why do we backup data ?
- you could delete files by accident
- your device can break down
- your device can get infected with a virus which will edit the data
- data can be corrupted by hackers
- ## your laptop could get stolen or damaged
why is it essential for business to backup their data ?
- business use computers to store very important data such ( customer record s, financial information , designs for products ) , so if this data is lost it could distrupt the business
how is personal backup made ?
- by burning data to a CD-R
- by copying the data to a USB stick
- by transferring the data to another computer in the network
how are business back up made ?
- they make backups daily
- they use large capacity devices such as magnetic tapes
- they automate the process so no one forgets to do it
- they keep old data just in case
- they keep the data off-site in case of fires or theft
