Storage Devices And Media

Storage Devices And Media

1. Backing Storage vs Main Memory

   • Main Memory
     • Also called RAM
     • used to store data temporarily
     • Data is allowed to be read back very quickly
   • Backing Storage
     • also reffered to as hard-drive
     • generally used to store data for a long time

2. Storage Media and Devices

   • device that holds data known as the storage medium
   • Storage media saves data that can be read and stored
   • The storage medium may be removable

3. Accessing Storage Data

   • Serial/Sequential access
     • stores files one by one
     • accessable in the order you recorded them
     • always and only serial access
   • Direct/random access
     • allows to be instantly accessed
     • a DVD is a random access device
     • DVD's are also directly accessable

4. Data storage capacity

   • storage is measured in bytes
   • it can store over a megabyte
   • modern harddiscs can store a terabyte or more

5. Data access speeds

   • There are fast and slow reading devices
   • speeds are measured in bytes per second
   • a hard drive can save/read at 300MBps

6. Magnetic storage devices

   • hard drives
     • fixed hard drives
       • bulit in hard drive
       • almost all computers have one
       • they are the main baking storage devices
     • portable hard drives
       • portable hard drive
       • they allow large amounts of data to be stored
       • many portable music devices have tiny hard drives
     • random access device
   • magnetic tape
     • A large capacity, serial access medium
     • needed for large files that has no need of quick access
     • also used in some batch-processing applications
   • removeable media magnetic dics
     • Zip discs
       • removeable and portable storage medium
       • large capacity random access discs
       • used for back up, or moving large files
     • Jaz discs
       • removable, portable medium
       • high capacity random access discs
       • used for moving large files
     • Floppy discs
       • removeable, low capacity disc
       • used to transfer small amount of data
       • nowadays they have been replaced by newer more intelligent technology

7. optical storage devices

   • read only optical discs
     • CD-ROM
       • compact disc may hold up to 800MB
       • not possible to delete
       • used to distribute all sorts of data
     • DVD-ROM
       • digital versatile disc may hold up to 4.7 GB
       • not possible to delete
       • stores high quality video
   • high capacity optical discs
     • Blu-Ray
       • can hold 25-50 GB of data
       • Blue ray comes from the ray color used
       • blue ray allows data to be placed closer together
     • HD DVD
       • high density DVD can hold up to 15 GB
       • random access devices
       • used to whatch high definition movies
     • DVD-RAM
       • A type of rewriteable DVD's
       • random access disc can hold up to 4.7 GB of data
       • much higher quality than normal DVD RW's

8. solid state storage devices

9. solid-state storage devices

   • USB Memory sticks
     • has made many other portable storage devides obsolete
     • non-volatile, random access storage device
     • many devices work as USB's when plugged in it appears as a drive
   • Memory cards
     • camaras, mobile phones, MP3 players they all use them
     • one of the most common formats used by digital camaras
     • a SIM card is as well a memory card
   • Smart cards
     • credit cards use chips and pin cards
     • limited amount of storage of the magnetic strip
     • flash cards are called smart cards

10. Backing Up Data

    • making one or more copies of data
    • Why backup your data?
      • If you delete by mistake you still have it elsewhere
    • How are backups created?
      • Burning files
      • copying files to external drive
      • copying files to other computer