Today i came across a sweet little tool that gives you information about disk size and usage. Discus is easily installed and is really handy for figuring out how much space is left on a server. Here's a screenshot of the install (sudo apt-get intall discus) and it's output.
After doing a little more looking, and RTFMing i realized that it was just a "prettier" version of df. Here are the two outputs.
To me they seem pretty much the same. Discus' bar graph is nice, but both give you a percent, although by default Discus' is a little more precise. df gives the ability to display file system type (-T) which i like, i also used the human readable (-h) tag which cleans up the output and makes it easier to read. One thing i couldn't find is a way to get either to display information on multiple hard drives. The server in the second screenshot has a second 100Gb hard drive but neither show it. i'm sure there is a way though...
The long and the short of it. you don't have to install anything for df, and the output is practically the same. so unless you really dig the graph and the blue headers don't bother with discus.
Cool site, love the info.