I remember one day I tried newer defraggler and it lagged like hell with initialization of drives and big lags on checking partitions so I didn't update. And then it didn't change in the next one and next one so I djust ignored updates all together. But now I feel there were many useful updates and decided to ask what was wrong and if that could be fixed with some settings or maybe there was a bug etc.
I have DF v2.21 and when changing between C:\ and D:\ drives, there is no lag.
Could you try portable version because that's what I use. This behavior is rock solid consistent on all notebooks I tried so far, just checked Thinkpad T410 (1st Gen I-core) in addition. Do you have v 2.16 archived somewhere for comparison? Because if not I can give you this one. 2-3 seconds of lag versus instant should be noticeable.
EDIT: just checked, standalone version shows same slowdowns at initialization drives on launch and on NO DATA when switching those in GUI. I really hope you could compare this behavior with older version. If you don't have one I can give uploaded 2.16 (clean and no .ini) but will understand if you won't risk using it though. https://mega.nz/#!dQZg1LxR!gWLOmaar-AWdiPHS5bUaMnppxK5abkZvPuQgan0zzsw
No, I don't use the Intel rapid storage driver, all the things it promises I don't need it to do for me.
The native driver MS use for the similar thing, I have not directly turned off, so if AHCI or native command queuing or any of the underlying MS operating services/driver are doing their thing, I have all that as is.
The 3 P's (power, performance and protection) that RST promotes are negated with latest gen hardware, SSD's and a good backup regime.
specs are; custom built from components, 7th gen Core i3 3.9GHz processor, 128GB NVMe Intel SSD, 1TB HDD, Gigabyte Z270 mobo, 16GB DDR4 RAM, and I built it about 6 months ago.