Aspects of storage
Capacity
The capacity of a storage device refers to how much data it is capable of storing. CDs allow storage of 700Mb, DVDs of 4.7Gb and external hard drives all the way up to 4Tb and beyond. As the quality of images, sound and video increases, we need more storage space to store them. So, over time, the capacity of these devices will continue to rise.
Speed
The speed of a storage device is also known as the data transfer speed. This is a measure of how quickly it can read and write data. This is measured per second and most devices have different speeds.
USB 3.0 is one of the fastest at this point in time, with speeds of 640 megabytes per second. At this speed it would take about 1.5 seconds to transfer an average-sized movie.
Rewritable, Recordable and Read Only
- R stands for Recordable. This means that data can be written on this device once and only once.
- RW stands for Rewritable. This means data can be written on this device and then changed several times.
- ROM stands for Read Only Memory. This means that the data on this device is permanent.
Deciding upon which device to use
When making a decision on the type of device that is most appropriate to use for backing storage it is important to consider:
- whether the device will be built in or portable
- does the device have enough storage space for the task that I need to use it for?
- is there appropriate interface support for this device?
For example, a DVD would not be suitable for use as the main backing storage device for desktop PCs. It would not be built in to the system and would not be able to store all of the data. Another example may relate to mobile phone use. A portable solid state SD card would be more appropriate for storing images than a portable hard disc drive. The portable hard disc would require an interface connection like USB 3.0 that would not be supported by the mobile phone.
