Transcript Topic 9 - Technical Implications

Computing Science
Information Systems Design and
Development
Technical Implications (Storage)
Learning Outcomes
By the end of this topic you will be able to:
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Describe distributed and off-line storage
Describe backup systems and strategies
Describe the functions of an interface
Describe different ways to classify backing
storage
Distributed and off-line storage
• Distributed storage is where data is stored on
more than one device and is replicated
• Data is managed by a distributed database
management system (DDBMS)
• DDBMS synchronises data across locations so
any change in one location is replicated across
system
• Allows multiple users to access data at same
time
Distributed and off-line storage
• Distributed storage used by companies like
Google and Facebook with very large numbers
of users across globe
• Impossible to store this amount of data on
single system
• Ensures data is backed up continuously – any
one centre that goes down is replaced by
another and has data restored when it is back
online
Distributed and off-line storage
• Offline storage is where data is physically
removed from system
• Very secure – cannot be ‘hacked’ or altered
• Can be used as way to physically transport
data
• Very difficult to update
Backup systems and strategies
• Essential that data is backed up in case system
fails
• Need to be able to both restore all data and to
re-install all OS and applications
• For individuals, using cloud based systems
gives an easy way to ensure backup
• Organisations with large amount of data need
a backup strategy to ensure data is secure
Backup systems and strategies
• Need a schedule of backups
• Three types of backup
• Full – all data is copied
• Differential – only data that has changed since last
full backup is backed up
• Incremental – only data that has changed since
last backup of any type is backed up
Interfaces
An interface is a connection between a computer and a
peripheral
Most common type of interface is USB (Universal Data
Bus)
• Designed to connect to multiple types of peripherals
• Allows both communication and receiving power supply
• USB3 is current up to date standard with data transfer rate
of 5Gigabits per second
Bluetooth is a wireless interface that allows data transfer
over short distances
Functions of an interface
• Buffering- data can be stored temporarily in an area of
memory called the buffer.
• Data format conversion - Converting data from serial to
parallel or from an analogue signal to a digital signal.
• Voltage conversion – changing from peripheral voltage to
processor voltage
• Protocol conversion - a standard that allows the connection,
communication and data transfer between computers and
peripherals.
• Handling of status signals - checks to see if devices are ready
to send or receive data.
Rewritable and Read only storage
• Rewritable storage is storage that can be saved to as many
times as possible. Data can be edited and deleted as required.
Discs would be marked CD-RW or DVD-RW
• Write – once storage is an older format where blank CD or
DVD discs can be used to store data but once the data is
stored it cannot be changed. Discs wold be marked CD-R or
DVD-R
• Read Only storage is storage that cannot be altered. Examples
would be a film stored on DVD or a music CD
Built in and removable storage
• Built-in storage - this is storage fitted inside a
computer. Devices cannot be used with other
devices. An internal hard drive would be an
example.
• External storage – this is storage separate from
the computer. Devices can be moved from
computer to computer. An external hard drive
would be an example
• Portable storage – this is storage that can easily
be moved from computer to computer. USB flash
drives would be an example
Magnetic and Optical Storage
• Magnetic storage devices store data on a
metallic coated surface.
• Hard discs and magnetic tape are examples of
magnetic storage
• Optical storage devices store data on a surface
with flat areas and recessed areas. These are
read by a laser
• CDs and DVDs are examples of optical storage
Solid state storage
• These are devices with no moving parts. Data
is stored on chips called EEPROMS (electrically
erasable programmable read only memory).
• They do not need power to keep data
• Common solid state storage includes
• Memory cards – in phones and cameras
• USB memory sticks
Solid state storage
Advantages of solid state storage
• They are small and so are easy to carry around.
• They are robust because they do not have any moving parts
• They use less power than hard drives, which means that batteries
can last longer in portable devices.
• They can be used with security software, passwords or fingerprint
scanners.
• They have fast access speeds.