Overview of secondary storage

• Secondary storage is a term that applies to a wide range of devices that provide persistent (permanent) storage for data files and applications. Secondary storage is non-volatile, so data is not lost when power is removed.
• Main memory is needed to store data and instructions during processing. Main memory is designed specifically for this purpose; it is high speed and can be accessed directly by location, however, it is expensive and volatile.

  By contrast, secondary storage needs to be high capacity and low cost. It needs to be fast enough for loading and saving files, and it needs to provide reliable permanent storage so that files are not lost or easily corrupted. The type of secondary storage chosen will depend on budget and how it is intended to be used.
• Secondary storage may be installed internally, i.e. inside the main system case. It can also be external, for example, a portable solid-state disk. External devices are often useful to transfer files from one computer to another, or where it is not possible to upgrade internal storage.
• Most computers will have at least one type of secondary storage. Rapid developments in technology have seen solid-state devices and embedded MultiMediaCard (eMMC) become commonplace, replacing magnetic hard disks and optical discs.
• There are three types of secondary storage that you need to be familiar with:

  • Magnetic (hard) disk
  • Solid-state disk
  • Optical disc