What is usually preferred in Kubernetes - having a one pod per node configuration, or multiple pods per node?
From a performance standpoint, what are the benefits of having multiple pods per node, if there is an overhead in having multiple pods living on the same node?
From a performance standpoint, wouldn't it be better to have a single pod per node?
The answer to your question is heavily dependent on your workload.
There are very specific scenarios (machine learning, big data, GPU intensive tasks) where you might have a one pod per node configuration due to an IO or hardware requirement for a singular pod. However, this is normally not a efficient use of resources and sort of eliminates a lot of the benefits of containerization.
The benefit of multiple pods per node is a more efficient use of all available resources. Generally speaking, managed kubernetes clusters will automatically schedule and manage the amount of pods that run on a node for you automatically, and many providers offer simple autoscaling solutions to ensure that you are always able to run all your workloads.
Running only a single pod per node has its cons as well. For example each node will need its own "support" pods such as metrics, logs, network agents and other system pods which most likely will not have its all resources fully utilized. Which in terms of performance would mean that selecting the correct node size to pods amount ratio might result with less costs for the same performance as single pod per node.
On the contrary running too many pods in a massive node can cause lack of those resources and cause metrics or logs gaps or lost packets OOM errors etc.
Finally, when we also consider auto scaling, scaling up couple more pods on an existing nodes will be lot more responsive than scaling up a new node for each pod.
