Osm2pgsql very slow way processing

When I do pbf dile import with Osm2pgsql it always gets stuck at ways processing. Id populates database with nodes rather quickly (the speed increaded when used "--drop" and "--disable-parallel-indexing" options, but ways are still processed at 0.16 kb/s. Now the server runs on a virtual machine with a fixed sized disk space. And the host system (windows 10) shows that there is a 50% disk usage while the ways are processed. What exactly is happening when ways are processed? Can using a normal mode (instead of slim) fix the issue? Would a normal mode map export be enough if I am not planning to frequently update database using --append (not gonna use it anyway, since it's slow to the point of being useless). Thank you.