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There are three different but related forms of fragmentation: external fragmentation, internal fragmentation, and data fragmentation, which can be present in isolation or conjunction. Fragmentation is often accepted in return for improvements in speed or simplicity. Analogous phenomena occur for other resources such as processors; see below.
Block suballocation addresses this problem by dividing up a tail block in some way to allow it to store fragments from other files. Some block suballocation schemes can perform allocation at the byte level; most, however, simply divide up the block into smaller ones (the divisor usually being some power of 2). For example, if a 38 KiB file is to be stored in a file system using 32
Fragmentation can be remedied by re-organizing files and free space back into contiguous areas, a process called defragmentation. Solid-state drives do not physically seek, so their non-sequential data access is hundreds of times faster than moving drives, making fragmentation less of an issue. It is recommended to not manually defragment solid ...
Operating systems may use different slab sizes and internal layouts depending on the size of the objects to be stored. The reason for the large slabs having a different layout from the small slabs is that it allows large slabs to pack better into page-size units, which helps with fragmentation.
Data thus structured are said to be blocked. The process of putting data into blocks is called blocking, while deblocking is the process of extracting data from blocks. Blocked data is normally stored in a data buffer, and read or written a whole block at a time. Blocking reduces the overhead and speeds up the handling of the data stream. [3]
The FAT file system is a file system used on MS-DOS and Windows 9x family of operating systems. [3] It continues to be used on mobile devices and embedded systems, and thus is a well-suited file system for data exchange between computers and devices of almost any type and age from 1981 through to the present.
However, there still exists the problem of internal fragmentation – memory wasted because the memory requested is a little larger than a small block, but a lot smaller than a large block. Because of the way the buddy memory allocation technique works, a program that requests 66 K of memory would be allocated 128 K, which results in a waste of ...
Unlike the Windows built-in defragmenter tool, Contig can defragment individual files, individual directories, and subsets of the file system using wildcards. Contig does not move any data except that belonging to the file in the question, so the amount it can defragment a file is limited to the largest contiguous block of free space on a system.