External HDD safe amount of free space?

[Canadian Ace]

hello all, I've been searching for some specific answers, but found none. My question is simple, How much "free space" must I leave on my external HDD (3TB, or 2.72 to be exact). I'm hoping if I leave say..3-5gb free it will still run okay and not have a high risk of failure, or fragmentation. And still copy at a normal USB 3.0 speed of course, I fully expect the files to load slower, and I should mention the files are all movies over 1gb in size.

Again, my question is, what's the safe amount of free space I should leave on a 3tb external HDD?

 

[volcanoscout]

You'll want to leave at least 5-10% free, otherwise it's going to bog down and you won't have space to defragment.

 

[ronintexas]

I try to keep between 10% and 25% free on a drive - the closer you get to max the higher the chance of an error.