AS ICT
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Identify suitable uses of common storage media
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understand the types of access and access
speeds required for each use (e.g.
serial/sequential, direct/random)
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Describe the comparative advantages and
disadvantages of using different backing storage
media
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What’s the difference between a storage
device and storage media?
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The media is where the data is stored – eg
the CD ROM, the magnetic tape, the barcode.
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The device is the equipment that is used to
store the data on the media – eg the CD
writer, the magnetic tape deck, the barcode
scanner.
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Magnetic
Optical
Solid state
Hybrid
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When you are working on a computer, the
data (and the programs) are stored in RAM.
However, this is volatile.
If you want your data to be available for
future use, you have to save it permanently
on some form of backing storage.
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Data is stored on these in the form of
magnetized bits.
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Magnetic
recording is a
backbone
technology of the
electronic age. It is
a fundamental way
for permanently
storing information.
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In the computer realm, magnetic recording is
used on floppy disks, hard disks and magnetic
tape as the main method for data storage.
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Magnetic data storage is popular because it is
an easy and inexpensive technology, with
good medium-term (10 to 20 years) storage
characteristics.
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These are very high capacity (can store
massive amounts of data)
A tape can be written to instantly and kept
for a long time, or the data can be erased and
the media used again and again. Bit for bit, it
is a much cheaper storage medium than CD-R
DVD or Blu-Ray.
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Data is stored on
the tape in the
order it is written:
Sequential - ie
record by record.
Retrieval is
therefore slow.
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Anywhere that
requires
extremely large
capacity data
storage where
speed of retrieval
is not an issue
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Batch processing: updating bank accounts
with cheques
Producing utility bills etc – all customers’
bills are produced at the same time, and
every record in the database has to be
processed
Making backups – every item of data has to
be read and saved
Payroll applications – all records have to be
processed in sequence and at the same time
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Bit for bit, cheaper than using
disks
Very robust – the tape is encased
in a cartridge
Easier to remove and keep away
from the computer than
equivalent storage media
Data transfer rate (ie putting the
data on) is very fast
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Access is very slow, so use is limited
Updating files requires a new tape to be
created.
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Industry standard for storing
data on a computer
Used for storing software files
and data files
Vary fast access to data, both
reading and writing
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Data is stored randomly on the surface of the
disk
Therefore access is Direct, or Random – this is
much faster than serial/sequential access.
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Any system that requires fast data access
times
Any system that requires fast data transfer
speeds
 Real-time systems eg robotics, rocket launching
etc
 Online systems eg booking systems, EPOS stock
control, EFT
 File servers in computer networks
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Fast data transfer rate
Fast data access times
Very large capacity
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Fixed hard disks are very easily damaged.
Often used as a backup
media
 Also used for
transferring large files
from one computer to
another
 Large capacity – 1TB is
now common
 Often used for
transferring server
software from one
network to another
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Fast data transfer rate
Fast data access times
Very large capacity
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If dropped, they are easily
damaged.
Transfer rats are not quite
as fast as fixed hard drives
More expensive than other
forms of removable media
(eg CDs, DVDs etc)
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All optical devices operate
by using a laser beam. The
laser reads from and
writes to the disk.
It etches the data onto the
surface as microscopic
‘pits’.
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Read Only Memory
Can only be read from
Cannot be written to
DVDs can store about 10x as
much as a CD
DVD writers use a shorter
wavelength of light, so pits are a
lot smaller and therefore more
data can be written onto a disk
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CD ROMs and DVD ROMs are used for
applications which require the prevention of
deletion of data (either accidental or
otherwise)
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Software
Computer games
Music albums
Reference books eg encyclopedias
Storing films
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DVDs hold more data than a CD
CDs are cheaper to buy than DVDs
Both hold much more data than a floppy disk
Both are cheaper than hard disks
Both are more robust than hard disks
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Data transfer rates are
slower than hard disks
Data access times are
longer than for hard disks