Storage Types and Devices

Storage Types and Devices

1. Types of access

   • Field
     • is an allocated space
   • Record
     • All of the data about something
   • File
     • When you put data together its likely to be stored in a fie

2. Why back up data?

   • To safeguard against loss of data due to the failure of the original secondary storage device; this could be due to hardware failure
     • EG: Head crash on a hard drive unit
     • Problems caused by files being overwritten accidentally
     • Possible corruption of files EG: caused by power surges
   • To safeguard against damage caused by hackers
     • They may not want to damage your info but they may want your info such as your bank account info
     • Hacking can cause problems such as corruption and data loss
   • Incase files need to be used elsewhere
     • This protects the originals against corouption or loss

3. Backing up data simply refers to the copying of files/ data to a different medium (disk, tape, flash drive, etc.) in case of a problem with the main secondary storage device.

4. Serial Access

   • When using serial access it is neccessary to start at the begginging of the file and then access each record in turn unntil the required record is found.
   • This is a very slow form of data access and is primarily used on magnetic tape systems
     • It is used in applications where speed of access or where the order in which the data is accessed isn't importnat
       • For example: Utility billing, clearing bank cheques or producing pay slips

5. Direct Access

   • This is used with magnetic disks, optical media and solid state media
     • The computer uses key field to calculate where the data should be stored, it then is able to access data from the calculated position
   • This is a much faster way to access data than serial access
   • When updating direct access the old records are just replaced by the new ones
     • It is not neccessary to sort records into any sepcifc order
   • This is used in applications where data access speed is vital
     • For example: In real time operations such as controlling a chemical plant

6. Secondary storgae devices

   • These ensure that data is tored permenantly so that it can be used again at a later date
     • There are three types of storage media, magnetic, optical and solid state
       • Magnetic: HDD, Portable hard disk drives , Magnetic tapes, CD/DVD disks, CD-ROM and DVD-ROM, CD-R and DVD-R, CD-RW and DVD-RW, DVD-RAM, Blue-ray discs
       • Solid state: Memory sticks / pen drives, flash memory cards, SSD