Fragmentation (computing)

In information technology, the dismemberment of a memory space is referred to as fragmentation. In contrast to internal fragmentation ( the waste ) is sometimes also referred to as external fragmentation.

Description

In many software systems, memory (RAM, disk space, etc ) ( eg to save to there data and be available ) as part of a dynamic hardware resource management programs as needed requested. These requests are served ( eg the operating system) by a sufficiently large storage area selected from the available pool of resources and is provided to the requesting program. Later this memory area to be returned and will be available the new requirements.

That is, there is a total of storage space from the areas which are currently in use and regions which are not used. If the ranges used not continuously one after the other, but still exist between pieces of free memory (fragments), one speaks of fragmentation or fragmented memory.

Fragmentation can cause failure of a memory request (and thus potentially to malfunction or even crash the program). This happens when a newly allozierender area is larger than the largest free fragment. Although in this scenario, the sum of the sizes of all unused fragments is at least as large as the allozierende to area, so there is enough total memory available, the request can not be serviced. So there are memory fragments which are not usable, even though they are not in use.

Examples

A familiar example is the fragmentation of file systems, which additionally have a performance disadvantage as a hard drive, multiple, scattered requests more time than sequential access.

Memory in the information technology that can be affected by fragmentation include:

  • Logical file systems
  • Physical disks
  • Physical memory (RAM)
  • Virtual Memory ( Virtual Memory Management )

Solutions

  • Increases the available memory space.
  • A storage virtualization ( Virtual Memory Management ) laminated fragmentation of physical RAM effectively.
  • Each allocation can only affect a single block of the same size, but what then leads to internal fragmentation: paging.
  • Defragmentation, mainly used for file systems on hard drives.
  • The number of unused fragments is reduced by displacement of the fragments used by adapting the references: Garbage Collection.
  • Memory management
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