FreeSpace lets you monitor and manage your drives
Over the years, a couple simple but popular genres of Mac Gems have been menu-bar utilities that let you easily eject mounted volumes (see Ejector, Semulov, Volumizer, and Undock); and menu-bar utilities that show you how much space is available on mounted volumes (see SpaceControl). Today’s Gem, FreeSpace 1.0 (Mac App Store link), combines aspects of both genres, making for a useful utility for monitoring your drives.
Like the aforementioned programs, FreeSpace runs as a systemwide menu. By default, it displays the free space on your boot volume; click FreeSpace's menu display and you'll see a list of every mounted volume—organized by type (local, external, disc, network, disk image and so on)—along with the amount of free space on each volume. If you’ve got a good number of drives and volumes, internal and external, this everything-at-a-glance menu is a convenient way to keep an eye on how much space you’ve got available.
If you’ve got multiple internal volumes, you can choose which of those volume’s free space appears in the menu bar. Just view the FreeSpace menu and move the cursor to the right of the desired volume’s free-space status; click the lock icon that appears.
One interesting note here: If you’ve got a laptop Mac, and you haven’t disabled mobile Time Machine backups (a Lion [Mac OS X 10.7] feature that saves backups to your local drive whenever your Time Machine volume is not available), the Finder and FreeSpace will likely show different amounts of free space on your startup drive. This is because the Finder’s free-space calculation ignores local Time Machine data—presumably because that space can be freed up automatically if needed—whereas FreeSpace considers that space to be in use. On my MacBook Air, for example, FreeSpace showed I had only 19GB of free space available, while the Finder claimed it was closer to 47GB. When I disabled local Time Machine backups—which also frees up any space previously used by local backups—FreeSpace’s display increased to mirror the amount of free space reported by the Finder.
FreeSpace also lets you eject any volume without having to open a Finder window or view the desktop. Just click the eject button next to a volume and it’s immediately unmounted; FreeSpace’s menu-bar display shows an eject icon when the volume has been unmounted successfully. (FreeSpace also displays a disk icon in the menu bar whenever a volume is mounted.)
If a connected drive has multiple partitions, unmounting one automatically unmounts all of them—you don’t have to deal with the Finder’s “Do you want to eject [volumename] only, or all the partitions?” dialog. Alternatively, click Eject All to quickly unmount all external volumes at once—convenient when you’re about to pack up your MacBook Pro for a road trip. (You of course can’t unmount your startup drive, and FreeSpace won’t let you unmount other internal volumes. If you want to unmount a non-startup internal volume, you’ll need to take a trip to Disk Utility.)
FreeSpace’s other simple-but-useful feature is that clicking on a volume name in FreeSpace’s menu opens that volume in the Finder. This is often quicker and more convenient than switching to the Finder and, if necessary, opening a new Finder window for navigating to that volume.
Unfortunately, FreeSpace won’t alert you if a particular volume is getting tight on space—that’s one of my favorite features of Space Control. And I wish you could save menu-bar space by showing only the FreeSpace icon in the menu bar, rather than a disk icon and the free space on one of your internal volumes. (The developer told me he's considering the latter feature for a future update.) Still, FreeSpace is handy for keeping an eye on your free drive space, as well as for quickly accessing and unmounting volumes.