Segments are moved for a variety of reasons. The most compelling among them is to make better use of disk freespace. Disk freespace is an unused contiguous extent of sectors on a disk that has been identified by EVMS as a freespace segment. A data segment can only be expanded by adding sectors to the end of the segment, moving the end of the data segment up into the freespace that immediately follows the data segment. However, what if there is no freespace following the data segment? A segment or segments could be be moved around to put freespace after the segment that is to be expanded. For example:
The segment following the segment to be expanded can be moved elsewhere on the disk, thus freeing up space after the segment that is to be expanded.
The segment to be expanded can be moved into freespace where there is more room for the segment to be expanded.
The segment can be moved into freespace that precedes the segment so that after the move the data segment can be expanded into the freespace created by the move.