Relations can also work across models, even across multiple controllers and clouds. These are called cross-model relations (sometimes just ‘CMR’) and they enable, for example, scenarios where your databases are hosted on bare metal, to take advantage of I/O performance, and your applications live within Kubernetes, to take advantage of scalability and application density.
A cross-model relation between two models, say Model A and Model B, can be:
- On the same cloud where the two models have the same controller, or
- On the same cloud, but with separate controllers, or
- On different clouds, where the controllers are also inherently separate (since a controller does not work with models across multiple clouds).
These three cases are illustrated below. The red line denotes the cross-model relation in each case.