74 lines
2.5 KiB
ReStructuredText
74 lines
2.5 KiB
ReStructuredText
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.. rhb1561120463240
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.. _about-persistent-volume-support:
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===============================
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About Persistent Volume Support
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===============================
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Persistent Volume Claims (PVCs) are requests for storage resources in your
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cluster. By default, container images have an ephemeral file system. In order
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for containers to persist files beyond the lifetime of the container, a
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|PVC| can be created to obtain a persistent volume which the
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container can mount and read/write files. In |prod-long|, |PVCs| are backed by
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Ceph.
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Management and customization tasks for Kubernetes |PVCs|
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can be accomplished by using StorageClasses set up by two Helm charts;
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``rbd-provisioner`` and ``cephfs-provisioner``. The ``rbd-provisioner``,
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and ``cephfs-provisioner`` Helm charts are included in the
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``platform-integ-apps`` system application, which is automatically loaded and
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applied when Ceph is configured.
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If ``platform-integ-apps`` is not applied, then enable Ceph. Enabling Ceph
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would automatically apply the ``platform-integ-apps`` application. For
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information on how to enable Ceph, see :ref:`Ceph Cluster on a Controller Host
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<ceph-cluster-on-a-controller-host>`.
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|PVCs| are supported with the following options:
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- with accessMode of ReadWriteOnce backed by Ceph |RBD|
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- only one container can attach to these |PVCs|
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- management and customization tasks related to these PVCs are done
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through the ``rbd-provisioner`` Helm chart provided by
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``platform-integ-apps``
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- with accessMode of ReadWriteMany backed by CephFS
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- multiple containers can attach to these PVCs
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- management and customization tasks related to these |PVCs| are done
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through the ``cephfs-provisioner`` Helm chart provided by
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``platform-integ-apps``
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After ``platform-integ-apps`` is applied the following system configurations are
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created:
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- **Ceph Pools**
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.. code-block:: none
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~(keystone_admin)]$ ceph osd lspools
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kube-rbd
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kube-cephfs-data
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kube-cephfs-metadata
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- **CephFS**
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.. code-block:: none
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~(keystone_admin)]$ ceph fs ls
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name: kube-cephfs, metadata pool: kube-cephfs-metadata, data pools: [kube-cephfs-data ]
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- **Kubernetes StorageClasses**
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.. code-block:: none
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~(keystone_admin)]$ kubectl get sc
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NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION
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cephfs cephfs.csi.ceph.com Delete Immediate true
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general (default) rbd.csi.ceph.com Delete Immediate true
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