This is NOT a question about how much free space to have on a "Startup," drive. This question is for a drive that DOES NOT have OSX installed on it. I routinely keep my storage drives no more than 90% full. (I know this may be overkill, as this is what is recommended for startup drives.) I just picked up a couple of 3tb Seagate Barracuda XT hard drives to store my HD video files. If I kept 10% free that would be 300gb! How much free space do I need to maintain on this drive? 10%, 300gb seems ridiculous. Is there another guide to how full a storage drive can be? Can I fill it to the rim? Does the size of the largest stored video file matter?