UltraDefrag is an open source disk defragmenter for Windows NT 4.0 and later operating systems. It makes use of the same defragmenting API used by many other windows defrag utilities, both open and closed source. However, UltraDefrag has two features that make it unique. The first is that it has a kernel mode driver that does most of the work. The second is the ability to run the application at boot up time in a manner similar to chkdsk. This allows for faster defragmentation time and the ability to defragment all files including system files.

UltraDefrag has the following features:

• Very fast defragmentation, the work is done via a kernel mode driver which has an optimal defraging algorithm.
• Ability to defragment system files.
• Very small engine written in pure C.
• Nice graphical interface - compact and functional.
• Safety, because the file moving is accomplished with Microsoft's own Defrag API.
• Simple to use.
• Ability to generate html reports of fragmentation status.
• Ability to include/exclude files based on simple filters.
• Native x64 support.
• Free: Distributed with full source code under the GNU General Public License.

UltraDefrag supports the following filesystems: FAT12/16/32, NTFS and on Vista UDF. UDF is a file system intended for optical media such as DVDs that unlike ISO9660, is rewriteable. It has also the ability to defragment volumes at boot time allowing you to move many system files that are always locked by the operating system. Currently all files besides the registry hives and the pagefile can be scanned at boot time. UltraDefrag can also defragment files and folders compressed by NTFS file system compression. And can even defragment floppies, although doing so is not particularly useful.

UltraDefrag runs on Windows NT 4.0, Windows 2000, Windows XP, Windows Server 2003 and Windows Vista, including 64 bit versions of Windows. NT 4.0 Alpha is not supported currently.

UltraDefrag can perform 3 jobs: Volume Analysis, Volume Defragmentation and Volume Optimization. Read carefully next chapters to understand how to run them. Here the appropriate algorithms will be discussed.

• Volume Analysis When the analysis job is requested, driver searches for files in specified directory. GUI program analyses all found files, because it needs a full information to redraw the cluster map properly. Console and native interfaces skips all unwanted files filtered out by user defined filters. Therefore these interfaces makes an analysis faster.
• Volume Defragmentation Program's engine defragments files by filling the free space areas at the beginning of the volume with fragmented files contents. To speed up this process, exclude unimportant files (temporary, archives and so on) using filters.
• Volume Optimization This job contains six steps:
  • Initial analysis. The defragmenter collects information about all files on the volume.
  • First optimization step. The program tries to become largest free space area at the beginning of the volume by moving all data from the beginning to the free space areas in the terminal part of volume.
  • Second analysis. This operation updates all information and frees temporarily allocated system space on NTFS.
  • Volume defragmentation. Fragmented files will be defragmented. As described above they will be placed in the leading free space areas, freed on the first optimization step.
  • Second optimization step. Unfragmented files will be moved to the beginning of the volume. They will be placed into the rest of the leading free space areas after files successfully moved at the previous step.
  • Final analysis. This operation updates all information.

  Note that Volume Optimization is very effective only when processed volume has a lot of free space. This is not a program's mistake, this is a cause of the Windows Defragmentation API imperfectness.

  Volume optimization algorithm works only on NTFS volumes, because FAT directories aren't moveable.

  NTFS file system is very imperfect. We cannot move internal files, such as $MFT, $Bitmap and other internal files with a '$' in the begginning of their names. This is a well known ntfs.sys driver's bug. Free space may be splitted into few small parts by such unmoveable internal files. So you may never become a large free space area to defragment pagefile and other big files. Though there are still two ways to achieve a full volume optimization:

  • The easiest way is very simple. Move all files from selected volume to another disk, than reformat the volume and move all files back. Works fine, except for system volumes that have locked files.
  • The second way requires an additional software: GParted Live CD (open source program) or Partition Magic (commercial software). First of all - reduce the selected volume size as much as possible. This operation will move all data to the beginning of the volume. All system files will be moved too (including $MFT, $Bitmap and so on). Next step - restore size of the selected volume. After this step we will have large contignuous free space area at the end of the volume. Final step - make a boot time defragmentation of the volume using UltraDefrag.