types of storage

• why do computers need secondary storage?

  -use the main memory(RAM)to store data and the instructions that are currently executed
• what is cache?

  small amount of main memory, very close to the CPU which stores frequently used instructions.
• what is volatile memory?

  It loses its contents when the computer / device is switched-off.
• what are the types of secondary storage?

  solid state devices

  optical storage devices

  magnetic storage devices
• examples of solid state devices?

  USB memory sticks
• examples of optical storage devices?

  CD, DVD, Blu-ray disc
• examples of magnetic storage devices?

  hard disk drives
• magnetic storage disks

  -use magnetic fields to magnetise tiny individual sections of a metal spinning disk.

  -Each tiny section represents one bit

  -A magnetised section represents a binary '1' and a demagnetised section represents a binary '0'. 

  -These sections are so tiny that disks can contain terabytes (TB) of data
• how does the magnetic storage disks work?

  -When the disk is spinning, a read/write head moves across its surface. 

  -To write data the head magnetises or de-magnetises a section of the disk that is spinning under it. 

  -To read data, the head makes a note of whether the section is magnetised or not.
• what are the advantages of magnetic storage disk?

  cheaper

  high capacity
• what are the disadvantages of magnetic storage disk?

  low reliability

  slow speed

  electromagnetic surge can corrupt/damage the data held.
• optical storage devices

  use a laser to scan the surface of a spinning disc made from metal and plastic.

  The disc surface is divided into tracks, with each track containing many flat areas and hollows. 
• how does optical storage work?

  1.When the laser shines on the disc surface,lands reflects the light back,whereas pits scatter the laser beam. 

  2.A sensor looks for the reflected light. 

  3.Reflected light - land - represents a binary '1', and no reflection - pits - represents a binary '0'
• types of optical storage?

  ROM media

  R(read)media are blank

  Read/Write
• advantages of optical storage

  can be transferred easily between computers

  cheaper
• disadvantages of optical storage

  can scratch easily(not durable)

  not much storage compared with other methods

  not reliable
• characteristics of solid state devices

  high cost

  much faster

  high capacity

  easily portable

  much durable than HDD
• cloud storage

  -The storage of data online in the cloud - means cloud storage

  -Data is stored on servers and can be accessed via the internet
• advantages of cloud storage

  data can be easily accessed

  backups and security

  additional storage can be accessed easily
• disadvantages of cloud storage

  -if you do it anywhere with internet,it can lead to hackers

  -if internet connection fails,you won't be able to access files

  -you are relying on other people to correctly secure your data and keep backups.

  -you don’t know if employees of the cloud service will have access to your data.