Information Systems Design and Development Technical Implications (Storage) Computing Science

Learning Outcomes By the end of this topic you will be able to: Describe distributed and off-line storage Describe backup systems and strategies Describe the functions of an interface Describe different ways to classify backing storage 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.