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I have a 900GB HDD that had around 120GB free. The disk was showing 55% fragmented so I ran a defrag.

The defragmentation took a long time and I left it running over the weekend, but unfortunately the process was interrupted. Now the disk is showing as 79% fragmented and it's completely full. I ran defrag again and it finished quickly (5 - 10 minutes) but the disk remained full and the fragmentation ratio remained at 79%.

FWIW, before running the defragger, I noticed that the disk was almost full (over 750GB) but adding up everything (by selecting everything on the drive and Alt+Enter) on the drive gave me a much lower number (around 300GB). Is it possible that there is some hidden data, a backup, or a snapshot that's taking up all the free space? Maybe another system snapshot was created when I ran the defragger, causing the disk to fill up?

I suspect that the computer was shutdown abruptly and that left some temporary files created by the defragger on the disk. Is there any way to recover from this? By recover I mean reclaim my free space and defrag the disk?

Giacomo1968
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ventsyv
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    My first thought is that chkdsk may help, at least to make sure that your files are still intact and may fix the allocated space as well. I would recommend you take an image of the disk first however. – Frank Thomas Sep 05 '18 at 17:16
  • Machine is booting up fine, all files seem to be in place, nothing is missing (other than the free space). – ventsyv Sep 05 '18 at 17:18
  • Unsure about the Windows world, but I wonder if there is a way to purge your caches. And running `chkdsk` might help too. – Giacomo1968 Sep 05 '18 at 17:20
  • Related question, but no accepted answer: https://superuser.com/questions/929999/defragmenting-using-defraggler-made-the-fragmentation-worse-and-increases-used?rq=1 – ventsyv Sep 05 '18 at 17:25
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    Running the built-in defragmentation tool does not "temporary files", so I also would suggest running `chkdsk`, like has been suggested by two other people. Your approach of selecting everything on the disk, to get the disk usage, is extremely flawed for numerous reasons. – Ramhound Sep 05 '18 at 17:29
  • What happens when you run http://bleachbit.sourceforge.net as an admin and clean away temp files? – K7AAY Sep 05 '18 at 17:31
  • might be worth looking for an open source disk treemap program, which allows you to very quickly see the worst offenders for space usage. In addition, look into the interaction between Volume Shadow Copy and defragmentation. – Yorik Sep 05 '18 at 17:31
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    @ventsyv - **DO NOT** run Bleachbit if you care about your files. You can use the Disk Cleanup utility and achieve the same result. Be sure to elevate the process to that of an Administrator. – Ramhound Sep 05 '18 at 17:32
  • "Is it possible that there is some hidden data, a backup, or a snapshot that's taking up all the free space? " - Is it possible the disk space is being used by a shadow volume, which cannot be detected, by selecting files. It could be, which is the reason, you should provide us that information on how much storage you have allowed for previous versions. Please edit your question to include this vital information required to answer your question. – Ramhound Sep 05 '18 at 17:32

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From your question I guess you used the Windows system defragger. To my knowledge, this system function does not move empty chunks. Try using a better defragmentation tool like Defraggler by CCleaner. It is free and even has a portable version. I've had good results with Defraggler so far, but, admittedly, have not had such high fragmentations, yet.

Do you have your pagefile on your fragmented HDD? If you have another HDD or partition, you could try moving your pagefile to another drive to get more space before you run defragmentation. You can move it back to the current drive after it has been properly defragmented

A disk tree mapper was mentioned in the comments to search for large files. WinDirStat (also free and portable) does exactly that. It indexes all the files in your specified directory and sorts them by size, so you can see what eats up most of your space.

Ian
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Turns out Windows search was filling up the disk. It doesn't seem that the defragger did anything bad. I'll run another defrag over the weekend.

ventsyv
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