About disk fragmentation

What is disk fragmentation

Disk fragmentation is generally described as files and free space being divided into separate chunks, which are scattered around the disk. This usually happens by deleting, truncating or extending files, which is done regularly during a files life. File fragmentation increases time needed for file access, since an additional time is needed to move drive's head from one file fragment to another. So, it decreases an overall system performance.

How to repair disk fragmentation

Defragmentation is the process used to correct disk and file fragmentation by concatenating the files into one contiguous chunk and consolidating free space. Disk defragmentaion eliminates the need to move drive's head from one file fragment to another, so it reduces amount of mechanical work needed to access files on disk. So, it speeds things up.

About the software

UltraDefrag is the first open source disk defragmenter for Windows which supports defragmentation of locked system files by running during the Windows boot process. Actually all files including registry hives and page-file can be defragmented at Windows boot time.

Also one of the primary goals of the UltraDefrag design is doing the job as fast as possible.

UltraDefrag aims to be also the most reliable and small disk defragmenter. We're trying to keep a reasonable balance between algorithms complexity and effectiveness.

UltraDefrag has the following features:

system files defragmentation (registry, page-file, ...)
MFT (master file table) defragmentation (on XP and later systems)
internal NTFS files defragmentation (on Windows 2000 and later systems)
ultra fast NTFS analysis
fast defragmentation algorithm
effective disk optimization algorithm (two strategies available)
safety, it can never damage processed files
simplicity, it can be used without reading the documentation
ability to defragment single files/directories from the context menu of Explorer
ability to defragment additional streams attached to NTFS files
ability to exclude any unimportant files based on flexible filters
ability to defragment files, which have more fragments than specified by a threshold
ability to automatically break defragmentation when the specified time interval elapses
ability to select multiple disks for defragmentation
well readable HTML reports
powerful command line interface
ability to automatically hibernate/shutdown PC after a job is done
ability to make an automatic effective defragmentation through Windows Task Scheduler
multilingual graphical interface
little binaries (less than 500 kb)
portable version available which requires no installation
native 64-bit support
open source code licensed under GPL

UltraDefrag runs on Windows NT 4.0, Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008 and Windows 7, including all 64 bit versions of Windows. NT 4.0 Alpha is currently not supported. ReactOS and Wine aren't supported yet, because they have no defragmentation API implemented at this moment.

UltraDefrag cannot be used on DOS, Windows 9x, Windows NT 3.51 and Mac OS since these operating systems provide no defragmentation API. However, Linux port of UltraDefrag exists. It is based on NTFS-3G capabilities.

Supported file-systems

The following file-systems can be defragmented by UltraDefrag: FAT12/16/32, exFAT and NTFS.

There are a few system restrictions which apply to disk defragmentation. Unfortunately UltraDefrag cannot take away these restrictions:

Directories on FAT disks cannot be moved. This is a well known FAT driver restriction and cannot be fixed.
The $Bitmap and other internal NTFS files cannot be defragmented on Windows versions prior to Windows 2000 and to defragment the $MFT file at least Windows XP is needed, because the NTFS system driver prevents accessing them.
The first 16 clusters of MFT cannot be moved on Windows XP and Windows Server 2003, this is a file system driver limitation. So, UltraDefrag skips $Mft file on these systems, if it contains two fragments only. In case of three or more fragments the file will be defragmented partially, if possible.
NTFS disks with a cluster size greater than 4 kilobytes cannot be defragmented on Windows NT 4.0 and Windows 2000.
On Windows NT 4.0 and Windows 2000 NTFS driver cannot move any part of the file - quite complex rules exist to define whether a part of the file can be moved or not. Due to the complexity of rules, UltraDefrag is not able to process NTFS disks so effectively as it does on Windows XP and later versions of Windows.

Never try to run UltraDefrag on NTFS v1.2 formatted disks under Windows NT 4.0, because this may crash your system. NTFS 1.2 had beta status and an appropriate system driver was not reliable.

Processing algorithms

Both optimization algorithms ignore any size, name and fragment count filters.

Defragmentation algorithm

The analysis phase scans the whole disk to collect information about all files and free space.
The defragmentation phase concatenates all fragmented files into one chunk. Files that can't be moved or are locked are skipped.
The partial defragmentation phase tries to concatenate the remaining fragmented files into as less pieces as possible.

Quick optimization algorithm

The analysis phase is the same as for defragmentation.
The next phase moves only fragmented files to the end of the disk to free space at the beginning of it.
The defragmentation phase is the same as for defragmentation.
The last phase tries to move as much not fragmented files to the beginning of the disk to create a big free space at the end.

Full optimization algorithm

The analysis phase is the same as for defragmentation.
The next phase moves all files, fragmented or not, to the end of the disk to free space at the beginning of it.
The defragmentation phase is the same as for defragmentation.
The last phase is the same as for quick optimization.

Another advantage of the described optimization algorithms over more complicated algorithms is their relatively small processing time.

Unfortunately the disk optimization algorithm works only on NTFS disks, because FAT directories are not movable.

On the other hand, NTFS disks are often logically split into several parts by files which cannot be moved ($Bitmap and others). Therefore it may be sometimes impossible to get a very large continuous free space area for, for instance, pagefile defragmentation. For such cases there are two workarounds available:

Move all files to another disk, reformat the disk and move all back. This causes the perfect disk optimization.
Run GParted or Partition Magic to manually reduce the disk size as much as possible. This operation will move all files including system files to the beginning of the disk. After restoring the original size, you will have a large continuous free space area at the end of the disk. This space may be used hereafter to defragment large files.

Note that UltraDefrag always skips files located directly in MFT records (these files usually have sizes below 1kb), because they are actually part of the MFT. Also files which have no content are skipped, because actually there are no clusters on disk belonging to them. Additionally, UltraDefrag never tries to defragment files marked as temporary by applications which created them. Because such files will be deleted soon, therefore they will not decrease the system performance.

Web resources

The Ultra Defragmenter's home page is at: http://ultradefrag.sourceforge.net

Please be sure to visit this site for information, documentation, tutorials, news, etc. All UltraDefrag related things are available there.

For help requests visit our forum: http://ultradefrag.sourceforge.net/forum

Please report all problems and bugs via our bug tracker: http://ultradefrag.sourceforge.net/bugs

To participate in UltraDefrag translation visit please WikiSpaces.com.

The most recent version of this handbook can be obtained from the program's SVN repository. Download the archive, unpack it, run the Doxygen tool and copy all files from the /rsc subdirectory to /doxy-doc/html. After these steps open /doxy-doc/html/index.html in your browser to view the latest version of the documentation.

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