When I've worked with datasets that size, the common operations tend towards the analytic or bulk operations, IME. That's not the sweet spot for an ORM, and SQL will often make a lot of sense. But, and again this is my experience, you often want to work with some more traditionally sized slice of that data, doing CRUDish things, and ORM can exist alongside the nicely tuned bulk or analytic operations. If you have the pure data operations side of a DB that size, I agree ORM isn't it.