Disk optimizer
Alternatively referred to as disk compression, a disk optimizer is a software program designed to organize data or compress data allowing the disk drive to contain the maximum amount of information as possible.
A good example of a disk compression software program is a Microsoft Windows utility known as double space.
With today's large hard disk drives, disk compression utilities are no longer used and no longer recommended. Generally, a disk compression utility should be used on hard disk drives of 1 gig and smaller.
The Microsoft Windows utility defrag can be considered a disk optimizer and is still commonly used and recommended even on large hard disk drives.
Also see: Defragmentation, Hard disk drive definitions