Volume purpose: decoupling storage from pods

• Otherwise storage lives & dies with pods

Pods lay claims to volumes and mount them. Can be used by multiple pods at the same time

• Native File & Block storage

Requirements

• Speed
• Replication
• Resiliency

Kubernetes only runs as a service. You need your own storage backend, whether it be S3 or EBS or whatever

Container storage interface (CSI) lets your system interface with the storage backend

Kubernetes Volume Subsystem

• Persistent Volume (PV)
• Persistent Volume Claim (PVC)
• Storage Class (SC)

CSI is out of tree

• All the code is decoupled from K8s and is on its own release cycle with other developers
• Developers can make CSI plugins