Running Disk Defragmenter has freed up over 30GB of free space!

I am not in the habit of running Windows Disk Defragmenter very often, but over the last few weeks I have been going through the process of importing my very large cd collection on to iTunes. My "C" Drive has a capacity of 222GB and I was down to 9.68GB of free space. I ran WDD but after 18 hours it had still not finished! I therefore decided to cancel the defrag, and after checking the capacity of my "C" drive, I found to my amazement that I now had 42.8GB of free space! I then downloaded the free Auslogics DiskDefrag and ran that. It completed in a few minutes and showed that the Windows Defrag had done most of the work but for some reason had failed to finish. Does anyone know why?

I have decided to disabled Windows Defrag and will use Auslogics version in future, as it gives information regards the progress of the defrag, and seems to be far more efficient and quick.

However, I am very surprised by the amount of free space that the defrag process has freed up. I have searched on various pc forums, and other posters have said the complete opposite to my own experience. The common consensus seems to be that defraging reduces the amount of free space on a disk rather than increase it!

There also seems to be a difference of opinion about how much free space one should leave on a hard disc to enable the pc to run efficiently. I was down to just over 4% before I defragged, but I have seen posts advising that one should leave betweeen 10% and up to 50% (which seems to me to be ridiculous!)

I would be grateful for any assistance that anyone can give me, in particular, why the defrag freed up (in my instance) so much free space.

[My operating system is Windows Vista (SP2)]

  lotvic 15:57 15 Feb 15

"Windows Defrag had done most of the work but for some reason had failed to finish. Does anyone know why?"

Yes, you said: "I ran WDD but after 18 hours it had still not finished! I therefore decided to cancel the defrag"

IMHO you should have at least 15% of free drive space for a defrag to run in. There is lots of file fragments swapping to be done :)

If you'd done the cleanup - empty temp files and recycle bin etc before you ran the defrag that would be some of the GBs reclaimed and then if your harddrive is very big and very fragmented it would do away with the numerous 'file fragment pointers/indexers' kbs and the 'empty' part of the blocks in each fragment (think of them as a box, you put part of a jigsaw in one box and part in another box etc, then pile the boxes up and it takes alot of space. Now put all the parts of the jigsaw into one box and - voilà you have lots of empty boxes available to pack something else in) and it would take a long time shuffling all that about.

I agree that you get more detail of what's happening in a defrag using the Auslogics version as MS took away the detail in Vista version. (They've put it back in again for W7 upwards)

  lotvic 16:00 15 Feb 15

Note: can I suggest you go into your profile on PCA forum and change your username as having your email on display will get you loads of SPAM emails.

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