drive4 won't fill up until all other drives fill up too, since Greyhole balance free space of all drives in the pool.Now my question is... when I copy files to my /movies folder, they are physically going on to my drive4. When Drive4 fills up, won't I encounter the same problem with having an insufficient landing zone?
ie when your landing zone will become small, it's because the total free space in your pool will be small too.
Still, you can use a higher 'min_free' value for that drive, so that even when all other drives are full, this one still has some free space, and thus will be filled to capacity last.
The min_free value is a greyhole.conf setting, but Amahi takes it from the database when it generates a new greyhole.conf.
So change it in the .conf, then install PHPMyAdmin or equivalent, go in the hda_production, in the table that I don't remember the name of (something about storage pool), and edit the drive4 row in there. Change the min_free value to 30g or something (from the default 10g).