Secondary Storage

Secondary Storage

1. non-volatile storage

   • Retains data when computer is switched off
   • Can store files and applications for later use

2. Magnetic Storage

   • Hard Disc Drives
   • Tape Drive
   • Often used for backing up data
   • Contains a set of magnetic components
     • North and South poles
       • Electromagnets read/write data
   • Characteristics
     • Low cost
       • Good value for money -more GB
     • Large capacity
       • 1-2 TB
     • Fast
       • Data can be read instantly
       • Data can be supplied in milliseconds
     • Not very portable
     • Moving parts
       • Decrease durability
     • Good reliability

3. Optical storage

   • CD's
   • DVD's
   • Characteristics
     • Laser used to read and data
       • Makes series of pits
     • Low capacity
       • CD's - 700MB
     • Good reliability
       • If not scratched
         • Decreases durability
     • Slow speed
     • Cheap
     • Quite portable - lightweight

4. Solid State Memory

   • Made of flash memory
     • Uses arrays of transistors
       • Switched using electrical signals
   • Solid State Drives
   • USB flash drives
     • SD cards
   • Characteristics
     • Very portable
       • Very reliable
     • Moderate capacity
     • Very fast
       • Can access data in nanoseconds
     • Expensive
     • Low Durabilty
       • Limited number of erase/write cycles