I was slightly annoyed that Defraggler (scheduled to defrag the drive in question twice a week) never managed to completely defrag one of my storage drives, 2Tb about 50% full. So I ran a manual defrag on the drive. It took about 16 hours to complete and afterwards there was 0% fragmentation and all file blocks were in perfect sequence - files at the beginning, free space at the end. I let the scheduled defrag setting remain active, though, for future purposes.
Today was a day for scheduled maintanance and I was wondering why my CPU fan kept revving all afternoon for no apparent purpose, until I checked Defraggler and discovered that the drive in question has been massacred fragmentation-wise. There was 0% fragmentation yesterday, and today 1 year-old large files have been torn apart into thousands of fragments. I had added some files to the drive - 20 or so RAW photographs - but in case they were fragmented, there was 40% free space to place them on the drive, without needing to rip apart non-fragmented 1Gb files.
1) I understand that when Defraggler sees fragmented files and is told to defragment according to schedule it performs some calculations of how to place the files on the drive. But with so much free space, why rip apart 1Tb of 0% fragmentation to defrag 160Mb of fragmented files?
This is extremely annoying since recently the scheduled defrag operations freeze my computer for a few seconds.