A "TreeMap" is a common method for visualising the data usage on a hard disk, the bounding rectangle reflects the overall size of the drive, and is subdivided into smaller sections based on the sizes of individual files and directories.
A "Sunburst" or "DaisyWheel" diagram is an alternative method
of representing the same thing, with the tree-like structure of the directories partitioning the disk.
A "Circle Packing" is another example of a visualisation that mixes size representations and hierarchical metaphors in a relatively well defined way.
Comparatively, I find the DaisyWheel delivers the most utility for disk-usage visualisation - but I think there's a better way even than that.
This idea is both a data-volume visualisation tool, but also with some extension could form an alternative interface into "Finder" or "Explorer" file and directory navigators.
The central drift draws on work by Maxime Causeret [see link below] where cell-like objects viewed from the top-down are caused to grow, as if on a petri-dish.
In this case, each cellular seed is determined by its position on the directory tree, its degree of "swell" determined by file/data content.
As the contents of the drive under review are read (or, if snapshots of the state of the drive are taken over time) the visualisation would spread and grow, quite organically, until such time as the limits of the petri-dish (or disk) are filled.
Making each object interactive, a scalpel-like mouse pointer could click and drag individual cells around, popping them through cell-membranes after a time-delayed pressure for relocation or deletion.
Similarly, regular or greppy expressions might be "washed" over the contents of a given petri-dish, staining or highlighting potential matches. These could then be copied, culled or otherwise examined for further analysis.
Setting parameters for the elasticness of cell-walls, and their propensity to fill the available space, and optional gentle pulsation amplitude and frequency might allow for some user-configuration.