Duc maintains a database of accumulated sizes of directories of the file system, and allows you to query this database with some tools, or create fancy graphs showing you where your bytes are.

Duc comes with console utilities, ncursesw and X11 user interfaces and a CGI wrapper for disk usage querying and visualisation.

Duc is designed to scale to huge filesystems: it will index and display hundreds of millions of files on petabytes of storage without problems.