HDD woke up without request

I’m facing weird thing… I close almost everything execept qmmp… say to my second HDD sudo hdparm -Y /dev/sdb go to sleep and it does. But after few minutes it will wake up! Why? Have user programs fro access to this. Qmmp actually play stream from internet… seems like some daemon trying to get access to my hdd. How to find which program does it??
I need some kind of iotop but with logging ability better if I can select which drive I want monitor.

It might be an index service like the one used for locate. Besides checking iotop I don’t have a better idea.