If desired, you can receive reports of usage on the filesystem. They consist of a du -s of all top level directories.

For example: 

    Fri Feb 25 01:01:38 EST 2000
    Filesystem            kbytes    used   avail capacity  Mounted on
    /dev/dsk/c1t1d0s0    2887603   62011 2767840     3%    /farm/project

    62001   /farm/project/fromme
    1       /farm/project/hinkley
    8       /farm/project/lost+found
They can be emailed nightly, weekly, or monthly.