It would be nice if storage units had a feature to distribute supplies equally among them. This would be especially nice with stockyards and root cellars.
Just as easy to build multiple storage facilities and then check the boxes of only what you want put in them.
I do make multiple storage facilities but, in my experience, they will fill up first from whatever is produced nearest them. I have my towns set to 1000 villagers so my towns get big. What I end up doing is having to start with the first stockyard/root cellar, and then move to the next nearest when it fills up. It would be nice to be able to spread everything evenly across the town.