Kubernetes Storage

• CSI is a storage interface for k8s
• List of CSI drivers Refer Here
  
• Refer Here for official docs of PVs
• Refer Here for official docs of Storage Classes
• Access Modes
  • RWO – ReadWriteOnce (Suitable for block storages like EBS, Azure Disk, Persistent Disk)
  • ROX – ReadOnlyMany (Any disk)
  • RWX – ReadWriteMany (Typically fileshares or blob storages)
  • RWOP – ReadWriteOncePod (Suitable for block storages like EBS, Azure Disk, Persistent Disk)
• Refer Here for using Azure Disk as PV

Lets create a mysql Pod where we create a persitent volume dynamically

• Refer Here for the changes done.
• Exercise: Try running mongodb with pvc and postgres with pvc

Necesity for database cluster

• To have HA we run database in multiple servers in the case of k8s multiple pods
• IN db cluster we have multiple servers and each server will have its own storage
• So we need to create pods and each pod should have its own persistent volume
• challenge to create cluster with deployments:
  • managing multiple PVs
  • pod names are not predictable: database clusters generally will have predictable endpoints (read endpoint, write endpoint)
• So we need a way to create
  • multiple pods and pvs
  • pod names should be predicatable
• all of the above are acheived with stateful sets