Fragmentation (data-processing)

The word Fragmentation in data processing can refer to:

the fragmentation of a Hard drive (or any other data carrier containing a Filing system)
the fragmentation of the memory:

Random access memory, to see low
virtual Memory, to see fragmentation of the virtual memory

In the data-processing networks, the fragmentation is the cutting of a package of data out of smaller packages, to pass through a bond of weaker MTU

The fragmentation of an hard drive

A computer comprises a Hard drive which itself comprises data.

It is said that an hard drive is fragmented when certain files which it comprises are not more only one block.

One needs then défragmenter the hard drive, using a utility dedicated to this task.

Example

Let us take again the example of Roberto Di Cosmo, while simplifying.

Let us compare the hard drive to a " large cupboard with tiroirs" , all of the same size, in which one would arrange files.

At the beginning, all the drawers are empty, and " the secrétaire" can fill the first drawers without problems. Files are withdrawn, which brings " trous" in the line of the drawers. A problem arises then when a file is too large to return of a draft in one of the empty sites. The file separate in several pieces then is then distributed in empty boxes.

Now, if the secretary must go to seek this file, it must go to seek a piece of it all on the left, then all on the right, then to find another piece in the medium… what is very expensive in execution time. In short, it is not the ideal: the solution is that, every week, " ten garçons" reorganize all the cupboard while placing the separate files side by side.

This operating process is currently used by the computers functioning under Windows, more precisely, it is the operating process of NTFS.

Fragmentation on the filesystem Ext2 (or Ext3)

August 1st

Fragmentation of the random access memory

Examples of techniques to reduce fragmentation:

The internal architecture of Malloc was conceived to reduce the fragmentation of the random access memory. There are several pools of plug, each pool corresponds to a different size of plug. There will be a pool for the plugs of less than 100 bytes, another for the plugs from 100 to 1000 bytes.

Fragmentation of packages