Helping people with computers... one answer at a time.

Defragging does not use up disk space; it only moves data around. That display you are looking at is at best an approximation of what's going on.

Running Defraggler by Piriform. Weekly after running a cleanup using Secunia, AVG 2012, Malwarebytes anti-malware and CCleaner, I defrag both machines using Defraggler (I like the graph they present). I notice on both machines that I have the graph of unused versus used changes with the USED getting larger and larger and the UNUSED getting smaller and smaller. If this continues, I'll run out of unused space in the future.

What's happening and I how can I regain disk space or fix this problem? Is this just Defraggler causing the problem? I know Win 7 has a defrag process but I've never used it, I don't think. I've not looked to see if it's turned on. Could both of them running cause the drain on the unused 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.

Article C5739 - August 26, 2012 « »

Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

1 Comment
August 28, 2012 10:13 AM

Hi Leo. W7Pro 64 bit. How to change time in the
task scheduler ? It is set for Wed 3:00 am and I
am shutdown.

Comments on this entry are closed.

If you have a question, start by using the search box up at the top of the page - there's a very good chance that your question has already been answered on Ask Leo!.

If you don't find your answer, head out to to ask your question.