If you drain a node in kubernetes the pods will be shut down all at once. This is not suitable if there is a quorum requirement as it will cause the application to have an outage. To get around this configure a Pod Disruption Budget.

The Pod Disruption Budget simple tells k8s that there needs to be a minimum number of pods available for a particular selector. This can be max unavailable or min available.

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: zk-pdb
spec:
  minAvailable: 2
  selector:
    matchLabels:
      app: zookeeper

https://kubernetes.io/docs/tasks/run-application/configure-pdb/