Obviously hard drive capacity is limited, especially on laptops. Using FileVault, I find that every few weeks, I need to restart, as my free hard drive space has been depleted with the things that I have been doing, and obviously, this munches into the available hard drive space. Furthermore, when restarting, the FileVault box which says "Would you like to free up the space? Although this may take a while and cannot be stopped, it is reccommended you do this now" appears. This dialog only seems to appear at certain times, and not on every restart, but I may have found a way to trigger it so that any free space that is still being used by FileVault but which is actually empty can be freed up:
- Run Disk Utility
- Select the disk on which you want to free up the space
- Choose the Erase tab, and click Erase Empty Space, and then pick the Zero Out Deleted Files setting. This will try to create files (I think to back some stuff up?) which usually tends to munch up the rest of the available hard drive. When this is done, restart, and then the FileVault space-recovering dialog should come up.
The only downside that I can see is that it may not work for large drives (ie. the files created may not fill up the entire disk), or that it may take an age to free up the space.
[
robg adds: I haven't tested this one.]