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docs/doc/source/usertasks/kubernetes/kubernetes-user-tutorials-about-persistent-volume-support.rst
Ngairangbam Mili 619c2e06d9 Changes for ceph-csi 3.9.0 (ds8) 
Updated the output of the kubectl get sc command (PROVISIONER and ALLOWVOLUMEEXPANSION columns)

Story: 2010688
Task: 48895

Change-Id: I68f2c04d86c02c076ae1d46809d38d3b950f6b0a
Signed-off-by: Ngairangbam Mili <ngairangbam.mili@windriver.com>
2023-10-05 14:26:56 +00:00

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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 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 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:

  • 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