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What You Will Learn
Advanced
- What StatefulSets are
- When to use them vs Deployments
- Stable identity and storage
A StatefulSet manages Pods with stable identities: stable hostname, stable storage, ordered startup/shutdown. Perfect for databases and distributed systems.
| Deployment | StatefulSet |
|---|---|
| Pods are interchangeable | Pods have unique identity |
| Random Pod names | Ordered: app-0, app-1, app-2 |
| Shared storage | Each Pod gets own volume |
| Best for: stateless apps | Best for: databases, queues |
When to use StatefulSet
Databases (MySQL, PostgreSQL, MongoDB), message queues (Kafka, RabbitMQ), distributed systems (Elasticsearch, Cassandra). Anything that needs stable identity or ordered startup.Terminalbash
# StatefulSet Pods have ordered names
kubectl get pods
# NAME READY STATUS
# mysql-0 1/1 Running
# mysql-1 1/1 Running
# mysql-2 1/1 Running
# Each has stable DNS name
# mysql-0.mysql.default.svc.cluster.local
# mysql-1.mysql.default.svc.cluster.localPractical Exercise
Understand: StatefulSet vs Deployment
Note: StatefulSet Pods are named app-0, app-1, app-2
Note: each Pod gets its own persistent volume
Think: which of your apps need StatefulSets?
Key Takeaways
- StatefulSet: stable identity, stable storage, ordered deploy.
- Pod names: app-0, app-1, app-2 (not random).
- Each Pod gets its own persistent volume.
- Use for: databases, queues, distributed systems.
- Deployment = stateless. StatefulSet = stateful.
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