Pod Disruption Budget (PDB): Setup, minAvailable & maxUnavailable Guide

Why Pod Disruption Budgets Matter

Without a PDB, running kubectl drain node-1 on a node can evict all replicas of your deployment simultaneously — causing a full outage. PDBs give you a declarative way to express availability requirements that the Kubernetes control plane enforces before any eviction.

PDBs apply to voluntary disruptions — operations that go through the Eviction API:

• Node drains (kubectl drain)
• Cluster Autoscaler scale-down events
• Kubernetes version upgrades (managed clusters)
• Node pool rotation
• Preemption of lower-priority pods

minAvailable vs maxUnavailable

PDB Manifest Examples

Basic PDB for a Deployment

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: myapp-pdb
  namespace: production
spec:
  minAvailable: 2
  selector:
    matchLabels:
      app: myapp

PDB for a StatefulSet (etcd / database)

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: etcd-pdb
  namespace: kube-system
spec:
  # etcd requires quorum: majority must be available
  # For 3 replicas, at least 2 must be available
  minAvailable: 2
  selector:
    matchLabels:
      component: etcd

Percentage-Based PDB (scales with HPA)

apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: api-pdb
spec:
  # At most 25% of pods can be disrupted at once
  # Works correctly whether HPA scales to 4 or 40 pods
  maxUnavailable: "25%"
  selector:
    matchLabels:
      app: api-server

PDB and Rolling Updates

PDB is separate from Deployment rolling update strategy (maxUnavailable in the Deployment spec). The Deployment field controls how the Deployment controller replaces pods during an image update. The PDB controls how many pods can be evicted by external operations (drain, autoscaler). Both constraints apply simultaneously.

Checking PDB Status

# List all PDBs in a namespace
kubectl get pdb -n production

# Detailed status: ALLOWED DISRUPTIONS column
kubectl get pdb myapp-pdb -n production
# NAME        MIN AVAILABLE   MAX UNAVAILABLE   ALLOWED DISRUPTIONS   AGE
# myapp-pdb   2               N/A               1                     2d

# Describe for selector and conditions
kubectl describe pdb myapp-pdb -n production

The ALLOWED DISRUPTIONS column shows how many pods can currently be evicted. If this is 0, kubectl drain will block until a pod becomes available.