The free space on your hard drive can be fragmented as well as your files.
Over time, as the system writes, modifies, and deletes files, the free space on the drive will be broken up into various bits and pieces scattered across your hard drive. This leads to further fragmentation: when the system writes a new file, it may have to break it up if it is too large for the largest continuous free space.
By defragmenting the free space on your hard drive, you can improve Windows' performance when writing new files. You'll also help prevent new files from being fragmented.
To defragment the freespace on your hard drive:
- In the Drive section at the top of the Defraggler window, right-click the drive to defragment, and then click Advanced.
- Click Defrag Freespace or Defrag Freespace (Allow fragmentation).
If you select Defrag Freespace, Defraggler will fill up free space chunks with whole files only. If you select Defrag Freespace (Allow fragmentation), Defraggler will use file fragments to fill up free space, though it will still try to reduce the number of total fragments on the drive.
You can also tell Defraggler not to move large files around while it's defragmenting free space. For more details, see this topic.
Which option should you use? If you want your free space to be as defragmented as possible, choose Defrag Freespace (Allow fragmentation). If you want to balance reducing the amount of fragmentation in your current files and free space, choose Defrag Freespace.