Storage devices

Storage devices

1. Magnetic storage devices

   • Hard drives
     • large capacity
     • random access
     • can store huge files
     • data accesses very fast
   • Fixed hard drive
     • build into the case of computer
     • main backing storage device
     • random access
     • high access speed
   • Portable hard drive
     • large amount of data can be stored
     • can be transported from computer to computer
     • portable
   • Magnetic Tape
     • large capacity
     • serial access medium
     • accessing individual files is slow
     • large amount of data can be stored
     • data back-up
     • batch-processing applications

2. Removable media magnetic discs

   • Floppy disc
     • removable
     • portable
     • cheap
     • low capacity storage medium
     • random access device
     • used to transfer only small amounts of data
     • access times are slow
     • obsolete
   • Zip disc
     • removable
     • portable
     • higher capacity of storage than floppy disc
     • similar in appearance to floppy disc
     • random access device
     • used for moving large files between omputers
     • used also to back up data
     • obselete
   • Jaz disc
     • removable
     • portable
     • large capacity
     • random access
     • data back up
     • moving large files between computers
     • expensive
     • unreliable
     • obselete

3. Optical storage devices/Media

   • High capacity optical discs
     • Blu-Ray
       • are recent replacement for DVDs
       • 25-50 GB
       • random access
       • stores high quality,HD video
       • higher storage capacity
     • HD DVD
       • 15 GB
       • random access
       • high quality,HD videos can be stored
       • abandoned
   • Read-only optical discs
     • CD-ROM
       • data cant be altered
       • random access
       • used to distribute data
       • can hold around 800MB
       • non-volatile
     • DVD-ROM
       • 4.7GB of data capacity
       • random access
       • can hold more data than CD-ROM
       • can store high-quality video
   • Recordable optical discs
     • CD-R and DVD-R
       • can have data burnt onto them
       • can not be erased
       • cannot remove data or re-use a full dics
     • CD-RW and DVD-RW
       • data burnt on them
       • erased
     • DVD-RAM
       • re-writable DVD
       • 4.7 GB
       • used in camcorders
       • used for video and data back-up and archiving

4. Solid-State storage devices

   • USB Memory Sticks
     • non-volatile
     • random access storage device
     • flash memory connected to a USB interface
     • add and erase files
     • move any type of file between files
     • cheap
   • Memory cards
     • compact
     • non-volatile
     • comes in a variety of shapes and sizes
   • Smart cards
     • reliable
     • cards with flash memory
     • large storage capacity