Why does defragging appear to lose disk space?

In this excerpt from
Answercast #47, I calm some worries that regular defragging of a hard drive
is using up disk space.

Losing disk space

Well, to begin with, there is no problem here. You are not actually losing
unused space. Defragging has no effect (and I mean zero effect) on how much
space is or is not used on a particular hard disk.

• All it does is it moves data around.

The Defraggler display

Now, what you’re seeing, I believe, is the impact of the fact that that
display (and I have to admit, I like Defraggler’s display as well, because it
tells me that things are going on), but that display is at best an
approximation of what’s going on.

Every little block, depending on how big you sized the window, reflects some
amount of disk space that may have both data and unused data in it.

• What the defragging process does is it coalesces those;

• It brings them all together (or it tries to at least) on a file-by-file
  basis.

So, it’s very possible that the appearance of that display, of that block
image display while defragging is going on, is fundamentally misleading to some
degree.

Defragging does not free up space

So I have to reinforce that defragging (and it doesn’t matter what tool you
are using):

• Defragging does not free up disk space:

• Defragging does not use disk space.

• All defragging does is moves the data around on the hard disk so that
  when it is accessed, it is accessed more quickly.

Windows 7 defragger

Now the one thing that I do want to mention is since you’re running
Windows 7, you are actually defragging more than you think you are.
It is not a problem.

• I want to say that again. It is not a problem;

• But Windows 7 by default will run a defrag on your hard drives once a
  week.

I believe it happens on Wednesdays, but I could be wrong. It could be
different for different systems. But if you actually look at the Task
Scheduler, you will find that Windows has a predefined task for defragging that
kicks off once a week.

Multiple defraggers

Now, if you happen to defrag more often than that using Defraggler, then
that’s fine.

• Again, they’re not in conflict;

• They’re not causing disk space to be used or not used;

• You’re just defragging a little bit more than you thought you were.

So, like I said, I don’t see a problem here at all and I think that what
you’re doing is fine. It’s more proactive and preventive maintenance than I see
most people doing, and I think it’s fine.