![FragmentationDefragmentation](https://upload.wikimedia.org/wikipedia/commons/d/d0/FragmentationDefragmentation.gif)
In the maintenance of
file system
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...
s, defragmentation is a process that reduces the degree of
fragmentation. It does this by physically organizing the contents of the
mass storage
In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. In general, the term is used as large in relation to contemporaneous hard disk drives, but it has been used large in relati ...
device used to store
file
File or filing may refer to:
Mechanical tools and processes
* File (tool), a tool used to ''remove'' fine amounts of material from a workpiece
**Filing (metalworking), a material removal process in manufacturing
** Nail file, a tool used to gent ...
s into the smallest number of
contiguous
Contiguity or contiguous may refer to:
*Contiguous data storage, in computer science
*Contiguity (probability theory)
*Contiguity (psychology)
*Contiguous distribution of species, in biogeography
*Geographic contiguity of territorial land
*Contigu ...
regions (fragments, ''extents''). It also attempts to create larger regions of free space using
compaction to impede the return of fragmentation. Some defragmentation utilities try to keep smaller files within a single directory together, as they are often accessed in sequence.
Defragmentation is advantageous and relevant to file systems on electromechanical
disk drives
Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are conside ...
(
hard disk drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...
s,
floppy disk drives
A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined w ...
and
optical disk media). The movement of the
hard drive's read/write heads over different areas of the disk when accessing fragmented files is slower, compared to accessing the entire contents of a non-fragmented file sequentially without moving the read/write heads to
seek other fragments.
Causes of fragmentation
Fragmentation occurs when the
file system
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...
cannot or will not allocate enough contiguous space to store a complete file as a unit, but instead puts parts of it in gaps between existing files (usually those gaps exist because they formerly held a file that the file system has subsequently deleted or because the file system allocated excess space for the file in the first place). Files that are often appended to (as with log files) as well as the frequent adding and deleting of files (as with emails and web browser cache), larger files (as with videos) and greater numbers of files contribute to fragmentation and consequent performance loss. Defragmentation attempts to alleviate these problems.
Example
![File system fragmentation](https://upload.wikimedia.org/wikipedia/commons/0/03/File_system_fragmentation.svg)
An otherwise blank disk has five files, A through E, each using 10 blocks of space (for this section, a ''block'' is an allocation unit of the
filesystem
In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...
; the
block size is set when the disk is formatted and can be any size supported by the filesystem). On a blank disk, all of these files would be allocated one after the other (see example 1 in the image). If file B were to be deleted, there would be two options: mark the space for file B as empty to be used again later, or move all the files after B so that the empty space is at the end. Since moving the files could be time-consuming if there were many files which needed to be moved, usually the empty space is simply left there, marked in a table as available for new files (see example 2 in the image). When a new file, F, is allocated requiring 6 blocks of space, it could be placed into the first 6 blocks of the space that formerly held file B, and the 4 blocks following it will remain available (see example 3 in the image). If another new file, G, is added and needs only 4 blocks, it could then occupy the space after F and before C (example 4 in the image).
However, if file F then needs to be expanded, there are three options, since the space immediately following it is no longer available:
# Move the file F to where it can be created as one contiguous file of the new, larger size. This would not be possible if the file is larger than the largest contiguous space available. The file could also be so large that the operation would take an undesirably long period of time.
# Move all the files after F until one opens enough space to make it contiguous again. This presents the same problem as in the previous example: if there are a small number of files or not much data to move, it isn't a big problem, but if there are thousands or even tens of thousands of files, there isn't enough time to move all those files.
# Add a new block somewhere else, and indicate that F has a second ''extent'' (see example 5 in the image). Repeat this hundreds of times and the filesystem will have a number of small free segments scattered in many places, and some files will have multiple extents. When a file has many extents like this, access time for that file may become excessively long because of all the random seeking the disk will have to do when reading it.
Additionally, the concept of “fragmentation” is not only limited to individual files that have multiple extents on the disk. For instance, a group of files normally read in a particular sequence (like files accessed by a program when it is loading, which can include certain
DLLs, various resource files, the audio/visual media files in a game) can be considered fragmented if they are not in sequential load-order on the disk, even if these individual files are ''not'' fragmented; the read/write heads will have to seek these (non-fragmented) files randomly to access them in sequence. Some groups of files may have been originally installed in the correct sequence, but drift apart with time as certain files within the group are deleted. Updates are a common cause of this, because in order to update a file, most updaters usually delete the old file first, and then write a new, updated one in its place. However, most filesystems do not write the new file in the same physical place on the disk. This allows unrelated files to fill in the empty spaces left behind.
Mitigation
Defragmentation is the operation of moving file extents (physical allocation blocks) so they eventually merge, preferably into one. Doing so usually requires at least two copy operations: one to move the blocks into some free scratch space on the disk so more movement can happen, and another to finally move the blocks into their intended place. In such a paradigm, no data is ever removed from the disk, so that the operation can be safely stopped even in the event of a power loss. The article picture depicts an example.
To defragment a disk, defragmentation software (also known as a "defragmenter") can only move files around within the free space available. This is an intensive operation and cannot be performed on a filesystem with little or no free space. During defragmentation, system performance will be degraded, and it is best to leave the computer alone during the process so that the defragmenter does not get confused by unexpected changes to the filesystem. Depending on the algorithm used it may or may not be advantageous to perform multiple passes. The reorganization involved in defragmentation does not change logical location of the files (defined as their location within the
directory
Directory may refer to:
* Directory (computing), or folder, a file system structure in which to store computer files
* Directory (OpenVMS command)
* Directory service, a software application for organizing information about a computer network's u ...
structure).
Besides defragmenting program files, the defragmenting tool can also reduce the time it takes to load programs and open files. For example, the
Windows 9x defragmenter included the Intel Application Launch Accelerator which optimized programs on the disk by placing the defragmented program files and their dependencies next to each other, in the order in which the program loads them, to load these programs faster. In Windows, a good defragmenter will read the
Prefetch
Prefetching in computer science is a technique for speeding up fetch operations by beginning a fetch operation whose result is expected to be needed soon. Usually this is before it is ''known'' to be needed, so there is a risk of wasting time by p ...
files to identify as many of these file groups as possible and place the files within them in access sequence.
At the beginning of the hard drive, the outer tracks have a higher data transfer rate than the inner tracks. Placing frequently accessed files onto the outer tracks increases performance. Third party defragmenters, such as MyDefrag, will move frequently accessed files onto the outer tracks and defragment these files.
Improvements in modern hard drives such as
RAM
Ram, ram, or RAM may refer to:
Animals
* A male sheep
* Ram cichlid, a freshwater tropical fish
People
* Ram (given name)
* Ram (surname)
* Ram (director) (Ramsubramaniam), an Indian Tamil film director
* RAM (musician) (born 1974), Dutch
* ...
cache, faster platter rotation speed, command queuing (
SCSI
Small Computer System Interface (SCSI, ) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interface ...
/
ATA TCQ or
SATA
SATA (Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard to ...
NCQ), and greater data density reduce the negative impact of fragmentation on system performance to some degree, though increases in commonly used data quantities offset those benefits. However, modern systems profit enormously from the huge disk capacities currently available, since partially filled disks fragment much less than full disks, and on a high-capacity HDD, the same partition occupies a smaller range of cylinders, resulting in faster seeks. However, the average
access time
Access time is the time delay or latency between a request to an electronic system, and the access being completed or the requested data returned
* In a computer, it is the time interval between the instant at which an instruction control uni ...
can never be lower than a half rotation of the platters, and platter rotation (measured in rpm) is the speed characteristic of HDDs which has experienced the slowest growth over the decades (compared to data transfer rate and seek time), so minimizing the number of seeks remains beneficial in most storage-heavy applications. Defragmentation is just that: ensuring that there is at most one seek per file, counting only the seeks to non-adjacent tracks.
Partitioning
A common strategy to optimize defragmentation and to reduce the impact of fragmentation is to
partition
Partition may refer to:
Computing Hardware
* Disk partitioning, the division of a hard disk drive
* Memory partition, a subdivision of a computer's memory, usually for use by a single job
Software
* Partition (database), the division of a ...
the hard disk(s) in a way that separates partitions of the file system that experience many more reads than writes from the more volatile zones where files are created and deleted frequently. The directories that contain the users' profiles are modified constantly (especially with the Temp directory and web browser cache creating thousands of files that are deleted in a few days). If files from user profiles are held on a dedicated partition (as is commonly done on
UNIX
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
recommended
files systems, where it is typically stored in the /var partition), the defragmenter runs better since it does not need to deal with all the static files from other directories. (Alternatively, a defragmenter can be told to simply exclude certain file paths.) For partitions with relatively little write activity, defragmentation time greatly improves after the first defragmentation, since the defragmenter will need to defragment only a small number of new files in the future.
Offline defragmentation
The presence of immovable system files, especially a
swap file
Swap or SWAP may refer to:
Finance
* Swap (finance), a derivative in which two parties agree to exchange one stream of cash flows against another
* Barter
Science and technology
* Swap (computer programming), exchanging two variables in the ...
, can impede defragmentation. These files can be safely moved when the operating system is not in use. For example,
ntfsresize
ntfsresize is a free Unix utility that non-destructively resizes the NTFS filesystem used by Windows NT 4.0, 2000, XP, 2003, Vista, 7, 8, 10, and 11 typically on a hard-disk partition. All NTFS versions used by 32-bit and 64-bit Windows ar ...
moves these files to resize an
NTFS
New Technology File System (NTFS) is a proprietary journaling file system developed by Microsoft. Starting with Windows NT 3.1, it is the default file system of the Windows NT family. It superseded File Allocation Table (FAT) as the preferred fil ...
partition. The tool
PageDefrag
PageDefrag is a program, developed by Sysinternals (now distributed by Microsoft), for Microsoft Windows that runs at start-up to defragment the virtual memory page file, the registry files and the Event Viewer's logs (files such as AppEvent.Evt, ...
could defragment Windows system files such as the swap file and the files that store the
Windows registry
The Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the registry. The kernel, device drivers, services, Security Accounts Manager, and use ...
by running at boot time before the GUI is loaded. Since Windows Vista, the feature is not fully supported and has not been updated.
In NTFS, as files are added to the disk, the
Master File Table
New Technology File System (NTFS) is a proprietary software, proprietary journaling file system developed by Microsoft. Starting with Windows NT 3.1, it is the default file system of the Windows NT family. It superseded File Allocation Table (FAT) ...
(MFT) must grow to store the information for the new files. Every time the MFT cannot be extended due to some file being in the way, the MFT will gain a fragment. In early versions of Windows, it could not be safely defragmented while the partition was mounted, and so Microsoft wrote a hardblock in the defragmenting
API
An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software Interface (computing), interface, offering a service to other pieces of software. A document or standa ...
. However, since
Windows XP
Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...
, an increasing number of defragmenters are now able to defragment the MFT, because the Windows defragmentation API has been improved and now supports that move operation. Even with the improvements, the first four clusters of the MFT remain unmovable by the Windows defragmentation API, resulting in the fact that some defragmenters will store the MFT in two fragments: The first four clusters wherever they were placed when the disk was formatted, and then the rest of the MFT at the beginning of the disk (or wherever the defragmenter's strategy deems to be the best place).
Solid-state disks
When reading data from a conventional electromechanical hard disk drive, the disk controller must first position the head, relatively slowly, to the track where a given fragment resides, and then wait while the disk platter rotates until the fragment reaches the head. A
solid-state drive
A solid-state drive (SSD) is a solid-state storage device that uses integrated circuit assemblies to store data persistently, typically using flash memory, and functioning as secondary storage in the hierarchy of computer storage. It is ...
(SSD) is based on
flash memory
Flash memory is an electronic non-volatile computer memory storage medium that can be electrically erased and reprogrammed. The two main types of flash memory, NOR flash and NAND flash, are named for the NOR and NAND logic gates. Both us ...
with no moving parts, so
random access
Random access (more precisely and more generally called direct access) is the ability to access an arbitrary element of a sequence in equal time or any datum from a population of addressable elements roughly as easily and efficiently as any othe ...
of a file fragment on flash memory does not suffer this delay, making defragmentation to optimize access speed unnecessary. Furthermore, since flash memory can be written to only a limited number of times before it fails, defragmentation is actually detrimental (except in the mitigation of
catastrophic failure
A catastrophic failure is a sudden and total failure from which recovery is impossible. Catastrophic failures often lead to cascading systems failure. The term is most commonly used for structural failures, but has often been extended to many oth ...
). However, Windows still defragments a SSD automatically (albeit less vigorously) to prevent the file system from reaching its maximum fragmentation tolerance. Once the maximum fragmentation limit is reached, subsequent attempts to write to disk fail.
Approach and defragmenters by file-system type
![Auslogics disk defrag](https://upload.wikimedia.org/wikipedia/commons/e/e8/Auslogics_disk_defrag.gif)
*
FAT
In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food.
The term often refers spec ...
:
MS-DOS 6.x and Windows 9x-systems come with a defragmentation utility called Defrag. The
DOS
DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems.
DOS may also refer to:
Computing
* Data over signalling (DoS), multiplexing data onto a signalling channel
* Denial-of-service attack (DoS), an attack on a communicatio ...
version is a limited version of Norton SpeedDisk. The version that came with Windows 9x was licensed from
Symantec Corporation
Gen Digital Inc. (formerly Symantec Corporation and NortonLifeLock) is a multinational software company co-headquartered in Tempe, Arizona and Prague, Czech Republic. The company provides cybersecurity software and services. Gen is a Fortune 50 ...
, and the version that came with Windows 2000 and XP is licensed from
Condusiv Technologies
Condusiv Technologies is an American software company based in Burbank, California. The company was formerly known as Diskeeper Corporation, a name derived from its flagship product, Diskeeper, a file-system defragmentation software package for ...
.
*
NTFS
New Technology File System (NTFS) is a proprietary journaling file system developed by Microsoft. Starting with Windows NT 3.1, it is the default file system of the Windows NT family. It superseded File Allocation Table (FAT) as the preferred fil ...
was introduced with
Windows NT 3.1
Windows NT 3.1 is the first major release of the Windows NT operating system developed by Microsoft, released on July 27, 1993.
At the time of Windows NT's release, Microsoft's Windows 3.1 desktop environment had established brand recognition ...
, but the NTFS filesystem driver did not include any defragmentation capabilities. In
Windows NT 4.0
Windows NT 4.0 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It is the direct successor to Windows NT 3.51, which was released to manufacturing on July 31, 1996, and then to retail ...
, defragmenting
APIs were introduced that third-party tools could use to perform defragmentation tasks; however, no defragmentation software was included. In
Windows 2000
Windows 2000 is a major release of the Windows NT operating system developed by Microsoft and oriented towards businesses. It was the direct successor to Windows NT 4.0, and was Software release life cycle#Release to manufacturing (RTM), releas ...
,
Windows XP
Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...
and
Windows Server 2003
Windows Server 2003 is the sixth version of Windows Server operating system produced by Microsoft. It is part of the Windows NT family of operating systems and was released to manufacturing on March 28, 2003 and generally available on April 24, 2 ...
,
Microsoft
Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...
included a
defragmentation tool based on
Diskeeper
Diskeeper is a discontinued defragmentation app, designed for Microsoft Windows. It was developed by Executive Software International, Inc., which later changed its name to Diskeeper Corporation, and is now called Condusiv Technologies. The fin ...
that made use of the defragmentation APIs and was a snap-in for
Computer Management. In
Windows Vista
Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...
,
Windows 7
Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on July 22, 2009, and became generally available on October 22, 2009. It is the successor to Windows Vista, released nearly ...
and
Windows 8
Windows 8 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on August 1, 2012; it was subsequently made available for downl ...
, the tool has been greatly improved and was given a new interface with no visual diskmap and is no longer part of Computer Management. There are also a number of free and commercial third-party defragmentation products available for
Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
.
*
BSD
The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...
UFS and particularly
FreeBSD
FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...
uses an internal reallocator that seeks to reduce fragmentation right in the moment when the information is written to disk. This effectively controls system degradation after extended use.
*
Btrfs
Btrfs (pronounced as "better F S", "butter F S", "b-tree F S", or simply by spelling it out) is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager (not to be confused ...
has online and automatic defragmentation available.
*
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...
ext2
The ext2 or second extended file system is a file system for the Linux kernel. It was initially designed by French software developer Rémy Card as a replacement for the extended file system (ext). Having been designed according to the same pr ...
,
ext3
ext3, or third extended filesystem, is a journaled file system that is commonly used by the Linux kernel. It used to be the default file system for many popular Linux distributions. Stephen Tweedie first revealed that he was working on extend ...
, and
ext4
ext4 (fourth extended filesystem) is a journaling file system for Linux, developed as the successor to ext3.
ext4 was initially a series of backward-compatible extensions to ext3, many of them originally developed by Cluster File Systems for ...
: Much like UFS, these filesystems employ allocation techniques designed to keep fragmentation under control at all times. As a result, defragmentation is not needed in the vast majority of cases. ext2 uses an offline defragmenter called
e2defrag
, which does not work with its successor ext3. However, other programs, or filesystem-independent ones such as defragfs, may be used to defragment an ext3 filesystem. ext4 is somewhat
backward compatible
Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially i ...
with ext3, and thus has generally the same amount of support from defragmentation programs. Currently e4defrag can be used to defragment an ext4 filesystem, including online defragmentation.
*
VxFS
The VERITAS File System (or VxFS; called JFS and OnlineJFS in HP-UX) is an extent-based file system. It was originally developed by VERITAS Software. Through an OEM agreement, VxFS is used as the primary filesystem of the HP-UX operating syste ...
has the
fsadm
utility that includes defrag operations.
*
JFS has the
defragfs
utility on IBM operating systems.
*
HFS Plus
HFS Plus or HFS+ (also known as Mac OS Extended or HFS Extended) is a journaling file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS 8.1 ...
introduced in 1998 with
Mac OS 8.1
Mac OS 8 is an operating system that was released by Apple Computer on July 26, 1997. It includes the largest overhaul of the classic Mac OS experience since the release of System 7, approximately six years before. It places a greater emphasis on ...
has a number of optimizations to the allocation algorithms in an attempt to defragment files while they are being accessed without a separate defragmenter. There are several restrictions for files to be candidates for 'on-the-fly' defragmentation (including a maximum size 20MB). There is a utility, iDefrag, by Coriolis Systems available since OS X 10.3. On traditional Mac OS defragmentation can be done by Norton SpeedDisk and TechTool Pro.
*
WAFL in
NetApp
NetApp, Inc. is an American hybrid cloud data services and data management company headquartered in San Jose, California. It has ranked in the Fortune 500 from 2012–2021. Founded in 1992 with an IPO in 1995, NetApp offers cloud data services ...
's ONTAP 7.2 operating system has a command called
reallocate
that is designed to defragment large files.
*
XFS
XFS is a high-performance 64-bit journaling file system created by Silicon Graphics, Inc (SGI) in 1993. It was the default file system in SGI's IRIX operating system starting with its version 5.3. XFS was ported to the Linux kernel in 2001; as ...
provides an online defragmentation utility called
xfs_fsr
.
*
SFS processes the defragmentation feature in almost completely stateless way (apart from the location it is working on), so defragmentation can be stopped and started instantly.
*
ADFS, the file system used by
RISC OS
RISC OS is a computer operating system originally designed by Acorn Computers Ltd in Cambridge, England. First released in 1987, it was designed to run on the ARM chipset, which Acorn had designed concurrently for use in its new line of Archim ...
and earlier
Acorn Computers
Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the United Kingdom, UK, including the Acorn Electron and the Acorn Archi ...
, keeps file fragmentation under control without requiring manual defragmentation.
See also
*
Comparison of defragmentation software
__NOTOC__
The following is a comparison of notable file system defragmentation software:
Notes
References
{{Reflist, 30em
External links
The Big Windows 7 Defragmenter TestThe Big Windows XP Defragmenter Test
Defragmentation softw ...
*
Fragmentation (computing)
In computer storage, fragmentation is a phenomenon in which storage space, main storage or secondary storage, is used inefficiently, reducing capacity or performance and often both. The exact consequences of fragmentation depend on the specific ...
*
File system fragmentation
In computing, file system fragmentation, sometimes called file system aging, is the tendency of a file system to lay out the contents of files non-continuously to allow in-place modification of their contents. It is a special case of data fragmen ...
*
Virtual disk image
A disk image, in computing, is a computer file containing the contents and structure of a disk volume or of an entire data storage device, such as a hard disk drive, tape drive, floppy disk, optical disc, or USB flash drive. A disk image is usua ...
*
Wear leveling Wear leveling (also written as wear levelling) is a technique Wear leveling techniques for flash memory systems. for prolonging the service life of some kinds of erasable computer storage media, such as flash memory, which is used in solid-state d ...
, a similar technique for prolonging flash memory content
Notes
References
Sources
* Norton, Peter (1994) ''Peter Norton's Complete Guide to DOS 6.22'', page 521 – Sams ()
* Woody Leonhard, Justin Leonhard (2005) ''Windows XP Timesaving Techniques For Dummies, Second Edition'' page 456 – For Dummies ().
* Jensen, Craig (1994). ''Fragmentation: The Condition, the Cause, the Cure''. Executive Software International ().
*
Dave Kleiman
Dave Kleiman (22 January 1967 – 26 April 2013) was an American computer forensics expert, an author or co-author of multiple books and a frequent speaker at security related events.
Craig Steven Wright claims Kleiman was involved in the i ...
, Laura Hunter, Mahesh Satyanarayana, Kimon Andreou, Nancy G Altholz, Lawrence Abrams, Darren Windham, Tony Bradley and Brian Barber (2006) ''Winternals: Defragmentation, Recovery, and Administration Field Guide'' – Syngress ()
* Robb, Drew (2003) ''Server Disk Management in a Windows Environment'' Chapter 7 – AUERBACH ()
External links
The Big Windows 7 Defragmenter TestBenchmarks of popular defrag utilities
Microsoft Windows XP defragmentation - How to schedule a weekly defragmentationhttps://archive.today/20130209083314/http://windowsitpro.com/article/articleid/77564/jsi-tip-6260-startdefrag-will-schedule-a-windows-2000-defrag-and-it-is-free-for-personal-use.html Microsoft Windows 2000 Professional and Server defragmentation - How to schedule defragmentation]
SST Hard Disk OptimizerHow Linux avoids making files fragmented
How defragmentation was changed for Windows 7Complete list of Defragmentation Utilities for Windows{{Webarchive, url=https://web.archive.org/web/20160528170217/http://www.fact-reviews.com/defrag/Defragmentation.aspx , date=2016-05-28
Defragmentation software
File system management
de:Fragmentierung (Dateisystem)#Defragmentierung in Betriebssystemen