Magnetic, Flash and Optical Storage Devices

Magnetic, Flash and Optical Storage Devices

1. Optical

   • examples include cds dvds and blue-ray discs
   • works by using a laser and by looking at reflections, determining where there are pits on a surface representing 1s and 0s
   • tend to be cheap to destribute and fairly resilient.

2. Magnetic

   • uses magnetisable material. Patterns of magnetisation are then used to represent binary sequences
   • examples include hard disk drives and magnetic tape (often used to back up servers)
   • tends to have a high capacity at a low cost
   • can be damaged if the device they are in is dropped or moved sharply while they are writing data

3. Flash

   • work by using a special type of ROM that can be overwritten
   • used in USB memory sticks and cameramemory cards
   • it can be read from and written to at high speeds
   • some hard disks now use flash memory.
   • solid state drives which are an alternative to a hard drive, but with no moving parts can use other technologies but most use flash
   • flash memory has no moving parts so cant be damaged in the same way magnetic hard drives can this also means it consumes less power than other media types
   • it is significantly more expensive
   • each storage location has a limited amount of times it can be written to ( usually up to 100,000 times but it depends on the quality of flash memory) to get around this most flash devices have a controller on board that moves frequently written-to files to different locations in the device
   • in the case of good quality SSDs, there is usually enough reserved extra space that can be used, such that the ssd will have a life expectancy to match a traditional magnetic hard drive