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 Persistent Volume Claim can be created to obtain a persistent volume which the container can mount and read/write files.
Management and customization tasks for Kubernetes PVCs 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 as part of the StarlingX installation.
PVCs are supported with the following options:
with accessMode of ReadWriteOnce backed by Ceph RBD
only one container can attach to these PVCs
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 PVCs 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:
~(keystone_admin)]$ ceph osd lspools kube-rbd kube-cephfs-data kube-cephfs-metadata
~(keystone_admin)]$ ceph fs ls name: kube-cephfs, metadata pool: kube-cephfs-metadata, data pools: [kube-cephfs-data ]
~(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