File system fragmentation: Difference between revisions

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[[File:FragmentationDefragmentation.gif|thumb|Visualization of fragmentation and then of defragmentation]]In [[computing]], '''file system fragmentation''', sometimes called '''file system aging''', is the tendency of a [[file system]] to lay out the contents of [[Computer file|files]] non-continuously to allow in-place modification of their contents. It is a special case of [[fragmentation (computer)#Data fragmentation|data fragmentation]]. File system fragmentation negatively impacts [[seek time]] in spinning storage media, which is known to hinder [[throughput (disk drive)|throughput]]. Fragmentation can be remedied by re-organizing files and free space back into contiguous areas, a process called [[defragmentation]].

[[Solid-state drive|Solid-state drives]]s do not physically seek, so their non-sequential data access is hundreds of times faster than moving drives', making fragmentation a non-issue. It is recommended to not defragment solid-state storage, because this can prematurely wear drives via unnecessary write–erase operations.<ref>{{Cite news |last=Fisher |first=Ryan |date=2022-02-11 |title=Should I defrag my SSD? |language=en |work=PC Gamer |url=https://www.pcgamer.com/should-i-defrag-my-ssd/ |url-status=live |access-date=2022-04-26 |archive-url=https://web.archive.org/web/20220218151612/https://www.pcgamer.com/should-i-defrag-my-ssd/ |archive-date=2022-02-18}}</ref>

==Causes==

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==Types==

File system fragmentation may occur on several levels:

* Fragmentation within individual [[computer file|file]]s

* Free space fragmentation

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The catalogs or indices used by a file system itself can also become fragmented over time, as the entries they contain are created, changed, or deleted. This is more of a concern when the volume contains a multitude of very small files than when a volume is filled with fewer larger files. Depending on the particular file system design, the files or regions containing that data may also become fragmented (as described above for 'regular' files), regardless of any fragmentation of the actual data records maintained within those files or regions.<ref name="ntfs-reserves-space-for-mft">{{cite web |title=How NTFS reserves space for its Master File Table (MFT) |url=https://learn.microsoft.com/en-us/troubleshoot/windows-server/backup-and-storage/ntfs-reserves-space-for-mft |website=learn.microsoft.com |publisher=Microsoft |access-date=22 October 2022 |language=en-us}}</ref>

For some file systems (such as [[NTFS]]{{efn|NTFS reserves 12.5% of the volume for the 'MFT zone', but ''only'' until that space is needed by other files. ''(i.e., if the volume ~ever~ becomes more than 87.5% full, an un-fragmented MFT can no longer be guaranteed.)''<ref name="ntfs-reserves-space-for-mft" />}} and [[Hierarchical File System|HFS]]/[[HFS Plus]]<ref name="diskwarrior-hfs-hfsplus">{{cite web |title=DiskWarrior in Depth |url=https://www.alsoft.com/in-depth |website=Alsoft |access-date=22 October 2022}}</ref>), the [[Collation|collation]]/[[Sorting|sorting]]/[[Data_compactionData compaction|compaction]] needed to optimize this data cannot easily occur while the file system is in use.<ref name="windows-2000-defrag-performance">{{cite web |title=Maintaining Windows 2000 Peak Performance Through Defragmentation |url=https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-2000-server/bb742585(v=technet.10) |website=learn.microsoft.com |publisher=Microsoft |access-date=22 October 2022 |language=en-us}}</ref>

==Negative consequences==