You could have downloaded Drive Monitor 4.1 for Mac from our application library for free. This free software for Mac OS X was originally created by Jude Giampaolo. The program is included in System Tools.
From the developer:
Drive Monitor displays information about volumes mounted to your computer, including which volumes are currently mounted, and how much space is being used on each of them. The main window shows the name and the icon of each volume, as well as their size, used space, free space, percent used, percent free, and a "thermometer" graphic representation.
You may want to check out more Mac applications, such as Stellar Drive Monitor for Mac, Brother Status Monitor or Hardware Monitor, which might be related to Drive Monitor.
HDD Management
Archivers