Storage

Storage

1. Primary storage

2. Secondary storage

   • Secondary storage refers to any storage- either internal or external to a computer
     • That is not under the direct control of the CPU
       • An example of internal secondary storage would be the hard disk.
       • An example of external storage would be a CD or an external hard drive.
       • Data that is directly under the control of the CPU is called primary storage.
         • An example of this would be RAM
   • A computer needs secondary storage to store data long-term
     • RAM is volatile memory.
       • Which means it contents are lost when the computer is turned off.
     • Secondary storage is needed to store the contents of RAM for when they are needed again at a later date
   • There are 3 types of secondary storage; these are optical, magnetic and solid-state.
     • Optical storage uses a lens and a light beam to read and write data onto a disk.
       • Examples of optical storage are CD, DVD and Blu-ray.
       • Advantages
         • Disks are portable.
           • Disks are cheap to manufacture.
             • Disks are fairly durable.
               • Some formats such as CD-R and DVD-R, means that data cannot be overwritten.
       • Disadvantages
         • The storage capacity of disks are relatively small compared to other storage devices.
           • In some cases, such as Blu-ray, a special drive is required to read/write the data to and from a disk.
     • Magnetic storage devices use magnets to record data on rotating metal plates.
       • An example of a magnetic storage is a hard disk drive.
       • Advantages
         • Large storage capacity.
         • Fast access to read and write data.
         • Fairly inexpensive to manufacture.
       • Disadvantages.
         • Data can be lost or altered by magnetic field or mechanical problems.
         • Can suffer wear and tear due to moving parts.
     • Solid-state storage uses flash memories to store data.
       • Examples of solid-state storage are solid-state drives, SD cards and USB memory sticks.
       • Advantages
         • Faster boot-up.
         • Can be made very compact in size.
         • Large storage capacity.