I run geth with the arguments below:
geth --fast --cache=1024 --datadir ./.ethereum
Now the datadir (.ethereum) takes more than 26Gb and the syncing process is continue. Is it OK? Because it looks like it try to download a whole database.
I've found many topics about that fast sync mode should take about 10 Gb of disk space. Maybe it is outdated? Is there anybody who have geth client working in fast sync mode? Could you please check the size of your datadir directory?
Geth version is 1.6.7 Startup logs: https://gist.github.com/ValeryDubrava/23faf1285981b6b37afe8d2c39eeb713