docs/doc/source/storage/kubernetes/about-persistent-volume-support.rst

About Persistent Volume Support

Persistent Volume Claims (PVCs) are requests for storage resources in your cluster. By default, container images have an ephemeral file system. In order for containers to persist files beyond the lifetime of the container, a can be created to obtain a persistent volume which the container can mount and read/write files. In , are backed by Ceph.

Management and customization tasks for Kubernetes can be accomplished by using StorageClasses set up by two Helm charts; rbd-provisioner and cephfs-provisioner. The rbd-provisioner, and cephfs-provisioner Helm charts are included in the platform-integ-apps system application, which is automatically loaded and applied when Ceph is configured.

If platform-integ-apps is not applied, then enable Ceph. Enabling Ceph would automatically apply the platform-integ-apps application. For information on how to enable Ceph, see Ceph Cluster on a Controller Host <ceph-cluster-on-a-controller-host>.

are supported with the following options:

• with accessMode of ReadWriteOnce backed by Ceph
  • only one container can attach to these
  • management and customization tasks related to these PVCs are done through the rbd-provisioner Helm chart provided by platform-integ-apps
• with accessMode of ReadWriteMany backed by CephFS
  • multiple containers can attach to these PVCs
  • management and customization tasks related to these are done through the cephfs-provisioner Helm chart provided by platform-integ-apps

After platform-integ-apps is applied the following system configurations are created:

• Ceph Pools

  ~(keystone_admin)]$ ceph osd lspools
  kube-rbd
  kube-cephfs-data
  kube-cephfs-metadata

• CephFS

  ~(keystone_admin)]$ ceph fs ls
  name: kube-cephfs, metadata pool: kube-cephfs-metadata, data pools: [kube-cephfs-data ]

• Kubernetes StorageClasses

  ~(keystone_admin)]$ kubectl get sc
  NAME               PROVISIONER     RECLAIMPOLICY VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION
  cephfs             ceph.com/cephfs Delete        Immediate           false
  general (default)  ceph.com/rbd    Delete        Immediate           false