As a first time user I was surprised to see how it works.
I read that it is supposed to be a single pass algorithm.
I tried to defragment a 3T disk 50% occupied.
At first DF moved all files to the upper part of the chart,
but that included all fragmented files too.
I even noticed that the fragmentation increased in the process!
Then, after many, many hours at 99% and 1 minute to go,
fragmented files were copied again to turn from red to blue.
But when the process finally was done, after another few hours,
I was left with 0% fragmentation, but many holes of free space,
so now I am doing a free space defragment.
So to me it feels like a 3-pass operation and files are copied three times.
Which costs obviously an enormous amount of time,
and a severe impact on the drive's heads, because the reading and writing is done on the same drive with bits and pieces.
Also I did not see much use of the memory, I have 16G, so a m2ts file of say 9G for instance completely fits in memory.
Quote from this site:
What Defraggler does
Defraggler scans the hard drive for folders and files that are scattered in non-contiguous clusters (clusters that aren't right next to each other).
Using a single-pass algorithm, it designs an optimum layout for these files so that Windows will spend the least amount of time retrieving them in the future.
Finally, Defraggler moves the files into this optimum pattern.
In my opinion the optimum pattern could have been achieved by directly placing the files without fragmentation in the right place,
and without leaving holes of free space.
Any other thoughts about this?