Input, Output, Storage

Input, Output, Storage

1. Storage

   • Magnetic Storage
     • Data recorded onto magnetic disks. Mechanical parts move over disks surface to read and write data.
   • Optical Storage
     • Data recorded onto optical disks. Lasers read and write data. Highly portable.
   • Solid State Storage
     • Data recorded onto solid state memory chips. Very durable and fast, no mechanical moving parts needed.

2. RAM + ROM

   • RAM
     • Usually quite large
     • Not as large as hard disks
     • Volatile
     • Used to store programs and data in use by the processor. This includes the operating system and application system.
   • ROM
     • Non-volatile
     • Usually quite small
     • Used to store the boot program (a small program which powers the operating system).
     • Used in embedded systems such as washing machines to store a program which can't be changed.
     • Some of the BIOS may be stored here but not the whole of it.
     • Programs stored here are called firmware.

3. Large Scale Storage

   • RAID
     • Redundant array of independant discs
       • Allows multiple HDDs to be bought together as a single drive.
       • Different types of RAID are used for different purposes.
         • RAID 0 Striped
           • Improved performance and more storage.
           • No fault tolerance, if one disk fails, RAID is destroyed.
         • RAID 1 Mirrored
           • Data is the same on each disk so if one fails it is on the other disks.
           • Lose half of your storage space, you need 2TB to get 1TB storage.
         • RAID 5 Striped Parity
           • Good fault tolerance and performance, failed disks can be recovered from parity files.
           • Needs at least three disks, space is lost to parity data.
           • Parity = a state of being equal, used to reconstruct data in the event of a disk failiure.
   • NAS
     • Network attached storage

4. Storage Area Network (SAN)

   • High speed network of storage devices.
   • Creates a virtual storage area out of lots of disks.
   • Excellent stability and performance.
   • Virtual Storage
     • Will abstract the type of storage in SAN, allowing devices to be added and removed without having to administer the individual devices.