Micro freeze on sector load.

Not sure if it’s the right section for those kinds of question, but since there’s no “technical” section…

While I’m walking in exterior areas, sometimes game freezes for a moment like it’s loading up area ahead. Sometimes it does it in interiors too, but very rarely. During that, I hear my HDD actively working. Is that suppose to happen? Does it load something from HDD, and what it might be?..

I also get random frame rate drops to 40-30 in huge moshpits, which is expectable, but still a little frustrating. By reducing Lighting to Low it really improved overall framerate, but I’m not sure it should be lagging at all.

What is the general take on this game’s optimization?

My specs:
Core i5 3.30GHz, 8 GB RAM, GTX 960 4GB VRAM, HDD 1TB, Win10

My HDD is relatively new one, bought few months ago, and I don’t have any slow OS loading or something similar in other games as in GD.