Persistent volumes and volume claims
A cluster administrator defines and creates a persistent volume (PV) to provide the cloud
infrastructure with the details of the implementation of the storage. Use Container Storage
Interface (CSI) drivers from platform-providers.
Security permissions for file systems are needed to secure the Kubernetes environment for the Cloud Pak and allow
workloads to access storage. Access modes describe how the nodes access the storage. Cloud Pak for Business Automation uses
ReadWriteOnce
(RWO) and ReadWriteMany
(RWX) depending on the
persistent volume.
To use a PV or a pool of storage that is defined in a storage class, a persistent volume claim (PVC) is needed to consume the storage resources. A PVC is a claim for storage by a user that can include requests for a specific size and access modes.
- If static volume provisioning is used, a cluster administrator must create PVs. The PVs describe
the real storage, which is available for use by cluster users when they create a PVC to bind to a
PV. For more information, see Static persistent volumes.The following example illustrates the YAML file contents to create a persistent volume claim. Use the example as a template for any PVC that you want to create statically.
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: <PVCName> namespace: <NAMESPACE> spec: accessModes: - ReadWriteMany resources: requests: storage: <Size> volumeName: <PVName> volumeMode: Filesystem storageClassName: <StorageClassName>
- Dynamic volume provisioning is a requirement of the Cloud Pak foundational
services. Storage classes are needed to meet the "slow", "medium", and "fast" file storage and block
storage for the Cloud Pak components. If you do not have three different file storage classes, you
can use the same one for "slow", "medium", and "fast". The cluster is asked to dynamically provision
a persistent volume specifically for the PVC when the PVC is created. For more information, see
Dynamic persistent volumes.Note: When the Cloud Pak for Business Automation operator asks for the PVC to be created, the dynamically provisioned PV is automatically bound to the PVC.