STORAGE

STORAGE

1. TYPES OF STORAGE

   • field
     • an allocated space
   • record
     • all the data about something
   • file
     • when you put data together , it is usually stored in a file.

2. WHY BACK UP STORAGE?

   • To safeguard against loss of data due to the failure of the original secondary storage device: this could be due to hardware failure, problems caused by files being overwritten accidentally or possible corruption of files
   • Safeguard damage caused by hacked. The very act of hacking in to files could cause problems such as corruption or data loss.

3. TYPES OF ACCESS

   • SERIAL ACCESS
     • It is primarily use on magnetic tape systems and is essentially a very slow form of data access. When the original magnetic tape ( the master file ) needs updating, an additional tape ( the transaction file) is required. The transaction file contains all the new data to allow the master file to be updated. The updated tape is referred to as the new master file.
   • DIRECT ACCESS
     • Direct access is used with magnetic disks,optical media and solid state media.Access is much faster than the serial access. When updating files using direct access, the old records/data are simply written over by the new records/data.

4. SECONDARY STORAGE MEDIA

   • Secondary storage devices ensure that data is stored permanently so that it can be used again at a later date.
     • Magnetic Storage Media
       • Hard Disk Drive
         • These are available on all computers and are the main method used for storing data.
         • Advantage(s)
           • They have a very fast data transfer rate and fast access times to data
           • They have very large memory capacities
         • Disadvantage(s)
           • Can be easily damaged if the correct shut down procedure is not carried out; this can lead to a head crash which would result in a loss of data
           • They have many moving parts when compared to, for example solid state drives (SSDs)
           • Their read / write operation can be quite noisy compared to SSDs
       • This depends on the magnetic properties of certain materials. Many hard disks drives are made up of more than one disk and these disks are known as platters.
       • Portable Hard Disks Drives
         • These devices work in much the same way as fixed had drives but are usually connected to the computer via the USB port and can be disconnected and used on different computers.
         • Advantages
           • The data access time and data transfer rate is very fast.
           • They have a large memory capacity
           • They can be used as a method of transferring information between
         • Disadvantages
           • They can be easily damaged if dropped or subjected to a strong magnetic field; as with fixed hard disk drives, an incorrect shut-down procedure could also lead to loss of data

5. Optical Storage Media

   • CD/DVD Disks
     • Described as optical storage devices. They us a single spiral track.