The Docs say...
A pod (as in a pod of whales or pea pod) is a group of one or more containers (such as Docker containers), the shared storage for those containers, and options about how to run the containers. Pods are always co-located and co-scheduled, and run in a shared context. A pod models an application-specific “logical host” - it contains one or more application containers which are relatively tightly coupled — in a pre-container world, they would have executed on the same physical or virtual machine.
But I'm unsure if "co-location" means on the same P̶o̶d̶ Node. When satellites are co-located they are "in close proximity so that to reception equipment on the ground they 'appear' to occupy a single orbital position." So, that could be on the same Cluster, not on the same Node.
At the time of posting this, the only info I can find on this issue is at https://platform9.com/blog/compare-kubernetes-vs-ecs/ where it says...
Containers in a single Pod are guaranteed to run on a single Kubernetes node.
Now that sounds pretty conclusive, but I haven't been able to get any corroboration on that anywhere. I want to make sure that they are correct and didn't just misunderstand and spread misinformation.
The reason I'm asking is that it seems like Kubernetes is inherently wasteful if this is true. It is almost certain that your nodes with pods deployed will have resources left over. It is likely that you will have a pod whose needs could be satisfied by the combination of these left over resources. However, if a pod cannot span multiple nodes, you will have to create a new node and have even more un-utilized resources.