Definition: defragment

To reorganize the hard drive by putting files into contiguous order. Because the operating system stores new data in whatever free disk space is available, data files become spread out across the platters as they are updated. Large files may be broken into hundreds of fragments, causing the read/write head to move back and forth numerous times to read the data. A "defragger" or "optimizer program" rewrites all the files and stores them in adjacent sectors. See platter.

Windows comes with the DEFRAG.EXE utility, which can be activated from the Start menu. Other popular defraggers, such as DymaxIO, formerly Diskeeper, offer enhanced capabilities. The Mac operating system performs degragmenting automatically.

Users Run the Gamut
Some users are fanatical about defragging their disks on a regular basis. Others rarely do it, if ever. After defragmenting, performance increases are most noticeable on very large databases that had been heavily fragmented. Because today's computers are so fast, users may not notice any increase in speed with routine applications such as word processing and spreadsheets, especially if files are small.

A Good Habit
Nevertheless, defragmenting disks regularly is good practice because it reduces wear and tear on the drive mechanism. In addition, should the hard disk ever crash and important files were not backed up, data recovery experts can restore a defragged disk more easily.

Before and After

This Diskeeper example, now DymaxIO, shows the fragmented files (in red) before defragging and the results below. This utility can be set up to defrag the disk whenever the machine is idle. As soon as the user clicks the mouse or presses a key, defragging is suspended.