[CentOS] Most efficient/fastest way to see disk usage

Hi all, I use this command to see disk usage: du -cks * | sort -rn | while read size fname; do for unit in k M G T P E Z Y; do if [ $size -lt 1024 ]; then echo -e "${size}${unit}\t${fname}"; break; fi; size=$((size/1024)); done; done

The data itself is around 200GB with lots of subdir and small files. The command takes for about 1 hour to finish.

Is there a faster way to see the disk usage of some directories?

Secondary objective is: To see which directories have changes (added/remove subdir/files) comparing to the previous data. I'm thinking of using "ls -laR" and "diff". But not sure.

Thank you.