Defragging after defragging

I defragged my drive, all nice and blue and stacked together, it was completed at 100%. Then, just for curiosity I tried with clicking on defrag again hoping it would just be instant 100% and surprisingly it started to defrag, moving out blue files, making red and, to sum up, defragging again.

Might this be a bug? Did defraggler found a new order the second time better than the first time? However that drive wasnt almost modified at all, its the storage drive which I would say not even the 0.5% of it was modified by me or other programs in the time the first defrag lasted.

Im tempted to try to press the button a third time, but it takes a couple of hours...

Nope, this is a windows thing. Windows begins refragmentation immediately even as a drive is being defragged (whether with defraggler or anything else)

Why would Windows fragment files deliberately without needing it? Just to be clear, it was the storage drive, not the drive where Windows is installed.

Why would Windows fragment files deliberately without needing it? Just to be clear, it was the storage drive, not the drive where Windows is installed.

maybe windows index service, maybe antimalware scan; hard to tell per se. and I could be wrong, but it's been my experience that just having a mounted drive could be enough

Im not sure about that. I have indexing service disabled. Also it seems that it was the own defraggler the one who fragmented the drive. It was blocky blue when I analyzed, then when I started it, it moved blue blocks to empty space to then put them again. I mean, it wasnt fragmented before the defrag.

I just did this too, and the same thing happened. Analysis showed my D partition was 100% defragged with no files in the fragmented list. I pressed defrag again expecting it to not move anything and finish immediately. An hour later, it's still moving things around. Obviously the 'optimum layout' that the algorithm makes during analysis is not definitively optimum!

I think I probably have the wrong idea about defragging though. I have two programs that my laptop struggles to run smoothly (Eg Space Engine), and one of the bottlenecks is reading from the disk fast enough. What I hoped defragging would do is put all the files pertaining to those programs right next to each other on the disk. Instead, defragging a disk seems to be more about trying to get each file wholly into one cluster (as opposed to spanning clusters), without any real attempt to optimise by collating related data.

If I want all the Space Engine files all to be put contiguously/adjacently in the same area of the disk, would the 'defrag folder' option do that?

I'm trying it right now, but it's taking a VERY long time - 6 fragmented files in 17 total fragments has taken over two hours, and I've still got 2 fragmented files in 5 fragments to go.

Thanks.