Expand Istio property replica counts to avoid problems when draining Istio nodes

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When draining Istio pods some nodes may not drain because they have a replica count of 1 , while 3 or more replicas are required. In order to avoid this, you should set the minimum replica count for each property to at least 3 .

When backing up and draining Istio nodes you may see errors like:

kubectl drain` failed to evict and reschedule pods to another node due to PodDisruptionBudget definitions:
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NAMESPACE NAME MIN AVAILABLE MAX UNAVAILABLE ALLOWED DISRUPTIONS AGE
istio-system istio-ingressgateway 1 N/A 2 5d11h
istio-system istio-pilot 1 N/A 2 5d11h
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For istio-ingressgateway and istio-pilot you can set the istio.ingressgateway.replicaCountMin and istio.pilot.replicaCountMin properties to 3 or higher. See the Configuration properties reference, istio .

For other istio components (that don't have a replicaCountMin property), see Manually upgrading a cluster or node pool in the GKE documentation or IstioOperator Options in the Istio documentation.