Ram working Keeping it fast

One phenomenon that many users of high performance computer notice is the  gradual deterioration in the speed of  access of their  disk drives over time. Many think that this is  a psychological effect, other  think that it is to do with the disk being too full. Neither of theses explanations is correct the slowing of  disk systems with use it  due to fragmentation. When you start using a  hard disk there is  generally plenty of unused space available in large contiguous chunks. This allow the operating systems to allocate  storage to files, even large files, so that they are stored in one  place of the disk. A file that is  stored using  sectors that are contiguous is fast to  read and write.

However  as the disk is  used free space is used up (and  also created) by the deletion  of files. Slowly but surely the free space becomes  broken up across the disk’s surface and eventually it isn’t possible for the operating  systems to find  chinks  of free space large enough  to store a file in one place.  In this case the file will be  stored using  two or more chunks  of free space – i.e  the file is stored using  non-contiguous  sectors.  This makes  the file  slower to read and write  because  the drive’s  heads have to be moved across the surface  of the  disk to read the  entire file . this is  fragmentation and its  effect can be a  dramatic  slow-down  in the operation of a disk. You van often tell a badly fragmented  disk by the sound or  the  head moving from track to track  as a file that is  scattered  across the surface  is retrieved. It gives the impression that the drive is  working hard for  simple file operations.

The solution to the problem is to reorganize the use of the  disk so that fragmented  files are stored  using contiguous sectors  and the free area  of the disk is  again composed of contiguous  sectors. The reorganization of the existing files results in an  immediate improvement in the read time  and the newly contiguous  area of free  space means  that fragmentation will not occur  again when files are created. Thus defragmentation improves , both read and write  times back to the  original performance  of the disk as  first delivered. Of course , as the  disk is used and files are  created and deleted fragmentation  will slowly develop but another session defragmentation soon cures that.