How to install processes that load Ubuntu 16.04 hard drive?

Question

linux

Updated from 14.04 to 16.04 and the first consequence is a relatively long download.
14.04 after booting up to the desktop barely using the hard drive, the system is completely ready to go.
16.04 booting to the desktop continues to diligently use the hard drive for another two minutes before the HDD indicator stops burning.
What could be the reason? How to set the source of such high i/o load?
And one more thing - what does the Ubuntu Software Center do on the system if it were to be replaced by Gnome Sowftware?
As advised, I used iotop.
Result - a python handicraft under the name gnome-sowftware slowed down the download. Disabled through regular autoload management.

Answer 1

iotop
atop