Kubernetes 09 - Storage in Kubernetes

Containers, by nature, are ephemeral. They’re designed to be easily created, destroyed, and replaced. This works great for stateless applications but poses challenges for applications that need to maintain state or store data persistently.

StatefulSets

One of the newer resource types in Kubernetes is StatefulSets. This resource type is designed to make Pods more “sticky.” In other words, StatefulSets help maintain the state and identity of Pods, which is crucial for stateful applications like databases.

It’s advisable to avoid stateful workloads in your first few deployments until mastering the basics of Kubernetes with stateless applications before diving into the complexities of stateful workloads. Whenever possible, consider using database-as-a-service offerings. These managed services can significantly simplify your infrastructure and allow you to focus on your application logic rather than database management.

Volumes

Kubernetes offers two primary types of volumes for creating and connecting storage:

1. Volumes

   • These are tied to the lifecycle of a Pod.
   • All containers within a single Pod can share these volumes.
   • They’re perfect for sharing data between containers in a Pod or for temporary storage that doesn’t need to outlive the Pod.

2. PersistentVolumes

   • These are created at the cluster level and can outlive a Pod.
   • They separate storage configuration from the Pod using it, allowing for more flexible and reusable storage solutions.
   • Multiple Pods can share PersistentVolumes, making them ideal for scenarios where data needs to persist across Pod restarts or be shared between different Pods.

The Future of Storage in Kubernetes: CSI Plugins

Container Storage Interface (CSI) plugins represent the new standard for connecting to storage in Kubernetes. These plugins provide a standardized way to expose arbitrary block and file storage systems to containerized workloads, making it easier to integrate various storage solutions with Kubernetes.