I'm trying to import a 240 GB Aperture library residing on a separate HD to the SSD main drive on my macbook pro. The plugin reports I have some 187 GB free where I'm in fact have 470 GB free. This misrepresentation of disk space makes it impossible to import.
What is going on? And, more to the point, how can this be fixed?
So I learned what the problem was. If you get info on SSD in Finder it reports one size which excludes space occupied by mobile backups. (a kind of Time Machine backups that resides on the same drive as the start up drive.) This space is not seen as available to softwares like Lightroom and hence it sees much less space available. The workaround is to temporarily disable this function, which requires a visit to the terminal. Then the space is truly freed up and available for the import of images.
You can also turn Time Machine off and that will delete the mobile backups, Time Machine Snapshots.
But to completely disable that, IMHO completely stupid, option you do have to do it from terminal.