About Persistent Volume SupportΒΆ
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 PVC can be created to obtain a persistent volume which the container can mount and read/write files. In StarlingX, PVCs are backed by Ceph.
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 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.
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 byplatform-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 byplatform-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 cephfs.csi.ceph.com Delete Immediate true general (default) rbd.csi.ceph.com Delete Immediate true