 If the fragments of a file are over 64 MB in size, the file is not defragmented if using the GUI; Microsoft has stated that this is because there is no discernible performance benefit since the time seeking such large chunks of data is negligible compared to the time required to read them.The result, however, is that "Disk Defragmenter" does not require a certain amount of free space in order to successfully defrag a volume, unlike performing a full defragmentation which requires at least 15% of free space on the volume.The command line utility, "Defrag.exe", offers more control over the defragmentation process, such as performing a full defragmentation by consolidating all file fragments regardless of size.