Size of an external drive?

Maybe I'm missing it. Is there a way to tell how much is used on the whole drive itself? Ultimately what I'm trying to do is have hazel send me a notification when my external drive reaches a certain size. I have a size rule but it applies it to the contents of the drive and not the drive itself. The only workaround I found was putting everything on the drive into 1 subfolder but that just seems silly.

You can have Hazel monitor the drive but note that that could become expensive. You can have it match anything under it and have a script which checks the disk size. You might need to do some other tricks but that should get you started. Again, though, it may end up being pretty resource intensive.

I see what you are saying. I was hoping there was a way to check the entire drive as a whole without having to write a script. If I do my little workaround of putting everything in one folder would it still chew up a lot of resources? then it's just checking the size of one folder, right?

Calculating the size of the folder may require scanning of everything below it. There may be some caching at different levels to alleviate some of this but fact remains that it potentially can be a resource hog. You can try it out and see how it works out for you.