Scripts/Tools to monitor drive usage?

[Daniel Swan-TM]

For the sake of capacity planning, I'd like to monitor my drive usage, and
find out at what times we are maxed, and for how long.  I'm thinking a combo
of a cron job that does a 'q mount' every 10 minutes, to gather the
information, and then using gnuplot or excel to plot it.

But before I go about this, I'd like to know if anyone out there has created
similar solutions they are willing to share.

Note:  We don't have the ADSM ODBC driver configured yet at our site.