StatefulSets and stateless Pods with Persistent Volumes (PVs) serve different purposes in Kubernetes, and their use cases reflect the fundamental differences between stateful and stateless applications.
StatefulSets
StatefulSets are designed for managing stateful applications that require stable, unique network identifiers, persistent storage, and ordered, graceful deployment and scaling. Here are the key characteristics and use cases of StatefulSets:
Stable Network Identifiers: Each pod in a StatefulSet has a stable, unique hostname and network identifier, which is crucial for stateful applications like databases that need consistent network identities to function correctly[1][2][5].
Persistent Storage: StatefulSets ensure that each pod has its own Persistent Volume Claim (PVC), which is linked to a specific pod. This means that even if a pod is rescheduled to a different node, it retains its storage, ensuring data persistence across restarts and rescheduling[1][2][5][11].
Ordered Deployment and Scaling: Pods in a StatefulSet are created, updated, and deleted in a strict, ordered manner based on their ordinal index. This ensures controlled scaling and rolling updates, maintaining the order and integrity crucial for stateful applications[1][2][5][11].
Use Cases: StatefulSets are ideal for applications that require stable storage and unique identities, such as databases (e.g., MySQL, MongoDB), distributed systems (e.g., Kafka, Zookeeper), and any application that needs to maintain state across pod restarts[1][2][5][11].
Stateless Pods with Persistent Volumes
Stateless Pods with Persistent Volumes, on the other hand, are used for applications that do not require stable network identities or ordered deployment but still need persistent storage. Here are the key characteristics and use cases:
Interchangeable Pods: In stateless applications, pods are fully interchangeable, meaning any pod can handle any request. This is suitable for applications where the state is managed externally, such as in a database, and the pods themselves do not need to maintain any state[1][2][5][11].
Persistent Storage: While stateless pods can use Persistent Volumes to retain data across restarts, the storage is not tied to specific pods. Instead, the PVs are shared among all replicas, and any pod can access the data[1][2][5][11].
