Secondary Storage

Secondary Storage

  • Secondary storage refers to non-volatile devices that store data on a permanent basis.
  • This is different from primary storage, such as RAM, which is temporary and volatile.
  • Primary storage is much faster, but secondary storage has a larger capacity.

Different Types of Secondary Storage

  • There are multiple types of secondary storage, including magnetic, optical, and solid state.
  • Magnetic storage includes hard disk drives (HDD) which store data on magnetized surfaces.
  • Optical storage includes CDs, DVDs, and BluRay discs, which use lasers to read and write data.
  • Solid state storage includes USB flash drives and Solid State Drives (SSDs), which have no moving parts and are generally faster.

Factors Affecting Choice of Secondary Storage

  • When choosing secondary storage devices, consider factors such as capacity, speed, portability, durability, and cost.
  • For instance, an SSD has faster read and write times than an HDD, but is typically more expensive for the same storage capacity.
  • Similarly, while a DVD may be a cheap way of storing data, it is not as robust or as easily transported as a USB flash drive.

Data Representation in Secondary Storage

  • Data in secondary storage is represented in binary form as a series of 0s and 1s.
  • These binary digits (or bits) are grouped together into bytes (8 bits).
  • The capacity of a storage device is typically measured in bytes, and prefixed with SI units, e.g. kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes (TB).

Hard Disk Drives (HDD)

  • Hard disk drives are a form of magnetic storage and consist of one or more rigid, fast rotating discs coated in magnetic material.
  • Data is read and written by a “head” that moves across the surface of the disc.
  • HDDs tend to have a larger capacity and lower cost than solid state drives, but are slower and more susceptible to damage due to their moving parts.

Solid State Drives (SSD) and Flash Storage

  • Solid state drives and flash storage are non-volatile storage devices with fast access times.
  • SSDs are similar to RAM but unlike RAM, they are not volatile.
  • SSDs and flash memory have no moving parts, making them more robust and less likely to fail due to physical shock.
  • However, they have a limited number of write cycles, meaning they can eventually wear out.

Optical Storage Devices

  • Optical storage devices, such as CDs, DVDs, and BluRay discs, read and write data using a laser.
  • They use less power and have longer lifespans than hard drives.
  • However, they have slower read and write times and typically have smaller capacities.