3. Storage devices and media Flashcards
What are ‘magnetic devices’?
Uses a magnetised surface area in order to hold bits of information
Fixed hard drive disk
Used on all computers / main method of storing data
Store operating systems, software applications and files.
Used in file-servers on computer networks to store files.
Advantages + disadvantages of fixed hard drive disk
ads:
Fast read
Huge capacities - thousands of movies and music files can be stored.
Easy to update and delete files.
disads:
Can easily be damaged when computer is not shutdown properly.
Not portable
Portable hard disk drive
Similar to ‘Fixed Hard Drive Disk’ but are connected to be computer externally.
Transportable
Has a USB cable to connect to the computer easily.
Comes with protective case to avoid damage.
Used to transport files from one device to another.
Advantages + disadvantages of portable hard drive disk
ads:
Small and light to carry around.
Designed to plug into almost every device that has a USB port.
Huge capacities.
Fast - direct data access.
disads:
Easy to misplace -> can be stolen easily.
Quite expensive compared to other ways to store data.
If dropped can still be damaged.
Floppy disc
Old method of storing data - information is held on a plastic thin disc.
Read / written by a floppy disc drive which rotates the disc.
Can still be used to transport very small files.
Advantages + disadvantages of floppy disc
ads:
Very light and easy to carry around.
Inexpensive.
disads:
Very low storage capacity compared to other media
Few modern computers have floppy disc drive.
Easy to damage
Transfers data very slowly
Magnetic tape
OLD
Data is stored in binary numbers.
Used to backup extremely large amounts of data.
Used where speed is not a priority.
Advantages + disadvantages of magnetic tape
ads:
Less expensive than the equivalent of hard disk drive.
Not easily damaged.
Very large storage capacities.
disads:
Slow data access / transfer (reading data back from the tape is slow.)
Needs another to update data
(e. g. original tape + tape with the changes = updated tape).
Optical storage media
Stores data on a disc as a number of data dots that can be read using light.
Data is read by shining the laser beam onto the surface of the disc.
In order to read / write data on a disc, you need a ‘disc drive’.
CD-ROM & DVD-ROM
‘Read only memory’
They are bought with pre-loaded data, meaning data is already on them (music, software, films and games)
Whatever is loaded on the disc cannot be removed or changed.
Advantages + disadvantages of CD-ROM & DVD-ROM
ads:
Hold more data than floppy discs.
Less expensive than Hard Disc Drives.
Cannot accidentally erase the file because it’s ‘read only’.
Very portable as they are small and light.
disads:
Holds less data than hard disk drives or memory sticks.
Slow data transfer and access rates when compared to hard disk drives.
Cannot add your own files to the discs.
CD-R & DVD-R
‘R’ = that disc is recordable once only.
Data can be added but not erased
Data is ‘burnt’ onto the discs using a disc burner.
CD-R’s: create personalised playlists of music.
DVD-R’s: store home recordings of video shot on a digital camera.
Can transfer data from one computer to another.
Advantages + disadvantages of CD-R & DVD-R
ads:
Impossible to accidentally delete
Cheaper than RW discs and Hard Disk drives.
Easy to transport information from one computer to another.
disads:
- Only recordable once / cannot be updated.
- If an error occurs during burning, the disc is damaged -> thrown away.
- Very slow data transfer rate.
- Not all CD / DVD players can read them.
CD-RW & DVD-RW
‘RW’ = Re-writable
Data can be added onto the disc and also be erased.
CD-RW: create personalised playlists of music and add / remove the songs as you wish.
DVD-RW: record television programmes and be recorded over many times.
Advantages + disadvantages of CD-RW & DVD-R
ads:
Can be re-used many times.
Data stored on the discs can be updated -> Not wasteful
disads:
More expensive than CD/DVD R discs.
Can accidently overwrite data.
Data transfer to the disc is very low compared to a hard disc drive.
DVD-RAM
DVD-Random Access Memory.
Rewritten over many many times.
Data writing + reading can happen at same time.
Can be reliably stored for many years because of their high quality.
They last long so they are frequently used in video and data archiving.
Advantages + disadvantages of DVD-RAM
ads:
- Long life - at least 30 years
- Can be written over 100,000 times
- Very fast
- Offer large storage capacity compared to CDs
- Read data at the same time it is being written
disads:
Expensive to other types of CDs and DVDs.
Don’t work in as many devices as the -R and -RW discs.
Blu-ray disc
Work in a similar way DVD ROMS but the laser used to read the data is blue rather than red.
Used to store high definition videos, home consoles, backup hard disk drive.
Advantages + disadvantages of blu-ray disc
ads:
Huge storage capacity - perfect for high definition videos.
Data can be read and transferred very fast when compared to other media.
disads:
Very expensive.
Only work in Blu-ray drives / players.
Solid state media
Have no moving parts.
Smallest form of data storage.
Store data binary codes.
Solid state hard drives (SSDs)
Used in desktop PC’s + laptops in place of magnetic hard disk drives
Use solid state technology based on electrical circuits so they have no moving parts.
Advantages + disadvantages of SSDs
ads:
Last longer than magnetic hard disks.
Faster data access/transfer times.
Use less power and produce less heat.
Run silently.
disads:
Smaller storage than magnetic hard disks.
More expensive than hard disks.
Memory sticks / pen drives
Used for transporting files / data between computers.
- Backing up data easily and quickly.
Advantages + disadvantages of memory sticks / pen drives
ads:
Small and lightweight.
Robust - less likely to become damaged.
Compatible with computers.
Large storage capacities
disads:
No write-protect feature - you can accidently cop over data.
Small physical size - easy to lose.
More expensive per GB
Flash memory cards
Known as SD cards - Secure Digital cards
Used to store photos on phones.
A wide range of devices have slots to read flash memory cards
Advantages + disadvantages of flash memory cards
ads:
Very small and so they are easy to transport files from one device to another.
Robust - not easily damaged.
Easy to connect to mobile devices through SD slots.
disads:
More expensive per Gb than magnetic hard drives.
Lower capacity than magnetic hard drives.
Small size - easily to lose.
You have to buy an SD card reader to connect to a PC.
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
Ads and Disads?
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
Ads and Disads?
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
Ads and Disads?
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
Ads and Disads?
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.
Ads and Disads?
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
Ads and Disads?
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
