A program from Executive Software called Diskeeper also performs disk defragmentation on computers running Windows NT. It supports both FAT and NTFS partitions. [Rul95]
The current version performs a simular optimization to what Windows 98 does. It monitors file usage, then moves the most frequently accessed data to the center of the disk in an attempt to reduce head movement time. [PS98] The original version of Diskeeper was designed for Windows NT 3.51 and was difficult to use. To make Diskeeper, Executive Software purchased a source license from Microsoft. A custom version of Windows NT 3.51 along with custom versions of NTFS and FAT were shipped with Diskeeper. To use Diskeeper, one had to install Executive Software's modified version of NT 3.51. [Rus]
Diskeeper monitors disk fragmentation through the use of a low priority NT service process constantly running in the background.[Pro95] [Rul95] During install the Setup program for Diskeeper patches four of the NT system files, including the NT kernel, in order to get the low-level file system information it needs. [Rul95]
The current version of Diskeeper is 3.0 as of this writing; however, Executive Software does have a version for free download called Diskeeper Lite that is somewhat less featured. Administrator priviledges are required for running the software.
To show how well Diskeeper works, Executive Software conducted a study using a dual Pentium 90 MHz computer and a single Pentium Pro 200 MHz computer. In both cases, the computers ran Windows NT Workstation 4.0. However, they tested partitions created by NT 3.51 as well as partitions created by NT 4.0 on each computer. Their results on the Dual Pentium 90 MHz computer showed that fragmentation caused the amount of time required to either read every file on the disk or read and write every file on the disk to increase to as much as double the original time. Their results on the Pentium Pro 200 were simular. Once the disk was fully defragmented, the amount of time required was almost as fast as the original time. They attribute the difference to fragmentation of the Master File Table, which can not be defragmented because it is held open by Windows NT for its exclusive use. [Int97c]