A cage[0] is ~100x larger than what you need to host a single server. Many data centers will colocate by the rack unit. At others you can get a quarter or half cabinet[1]. Even at the very largest enterprise datacenters you can colocate a single cabinet.

[0]: https://static.cisco-eagle.com/images/category/WireCrafters/...

[1]: https://www.edpeurope.com/wp-content/uploads/EDP-3-Compartme...