Chapter 6. Configure storage for OpenShift Container Platform services

You can use OpenShift Container Storage to provide storage for OpenShift Container Platform services such as image registry, monitoring, and logging.

The process for configuring storage for these services depends on the infrastructure used in your OpenShift Container Storage deployment.

Warning

Always ensure that you have plenty of storage capacity for these services. If the storage for these critical services runs out of space, the cluster becomes inoperable and very difficult to recover.

Red Hat recommends configuring shorter curation and retention intervals for these services. See Configuring the Curator schedule and the Modifying retention time for Prometheus metrics data sub section of Configuring persistent storage in the OpenShift Container Platform documentation for details.

If you do run out of storage space for these services, contact Red Hat Customer Support.

6.1. Configuring Image Registry to use OpenShift Container Storage

OpenShift Container Platform provides a built in Container Image Registry which runs as a standard workload on the cluster. A registry is typically used as a publication target for images built on the cluster as well as a source of images for workloads running on the cluster.

Follow the instructions in this section to configure OpenShift Container Storage as storage for the Container Image Registry. On Google Cloud, it is not required to change the storage for the registry.

Warning

This process does not migrate data from an existing image registry to the new image registry. If you already have container images in your existing registry, back up your registry before you complete this process, and re-register your images when this process is complete.

Prerequisites

  • You have administrative access to OpenShift Web Console.
  • OpenShift Container Storage Operator is installed and running in the openshift-storage namespace. In OpenShift Web Console, click OperatorsInstalled Operators to view installed operators.
  • Image Registry Operator is installed and running in the openshift-image-registry namespace. In OpenShift Web Console, click AdministrationCluster SettingsCluster Operators to view cluster operators.
  • A storage class with provisioner openshift-storage.cephfs.csi.ceph.com is available. In OpenShift Web Console, click Storage → Storage Classes to view available storage classes.

Procedure

  1. Create a Persistent Volume Claim for the Image Registry to use.

    1. In the OpenShift Web Console, click StoragePersistent Volume Claims.
    2. Set the Project to openshift-image-registry.
    3. Click Create Persistent Volume Claim.

      1. From the list of available storage classes retrieved above, specify the Storage Class with the provisioner openshift-storage.cephfs.csi.ceph.com.
      2. Specify the Persistent Volume Claim Name, for example, ocs4registry.
      3. Specify an Access Mode of Shared Access (RWX).
      4. Specify a Size of at least 100 GB.
      5. Click Create.

        Wait until the status of the new Persistent Volume Claim is listed as Bound.

  2. Configure the cluster’s Image Registry to use the new Persistent Volume Claim.

    1. Click AdministrationCustom Resource Definitions.
    2. Click the Config custom resource definition associated with the imageregistry.operator.openshift.io group.
    3. Click the Instances tab.
    4. Beside the cluster instance, click the Action Menu (⋮)Edit Config.
    5. Add the new Persistent Volume Claim as persistent storage for the Image Registry.

      1. Add the following under spec:, replacing the existing storage: section if necessary.

          storage:
            pvc:
              claim: <new-pvc-name>

        For example:

          storage:
            pvc:
              claim: ocs4registry
      2. Click Save.
  3. Verify that the new configuration is being used.

    1. Click WorkloadsPods.
    2. Set the Project to openshift-image-registry.
    3. Verify that the new image-registry-* pod appears with a status of Running, and that the previous image-registry-* pod terminates.
    4. Click the new image-registry-* pod to view pod details.
    5. Scroll down to Volumes and verify that the registry-storage volume has a Type that matches your new Persistent Volume Claim, for example, ocs4registry.

6.2. Configuring monitoring to use OpenShift Container Storage

OpenShift Container Storage provides a monitoring stack that comprises of Prometheus and Alert Manager.

Follow the instructions in this section to configure OpenShift Container Storage as storage for the monitoring stack.

Important

Monitoring will not function if it runs out of storage space. Always ensure that you have plenty of storage capacity for monitoring.

Red Hat recommends configuring a short retention interval for this service. See the Modifying retention time for Prometheus metrics data of Monitoring guide in the OpenShift Container Platform documentation for details.

Prerequisites

  • You have administrative access to OpenShift Web Console.
  • OpenShift Container Storage Operator is installed and running in the openshift-storage namespace. In the OpenShift Web Console, click OperatorsInstalled Operators to view installed operators.
  • Monitoring Operator is installed and running in the openshift-monitoring namespace. In the OpenShift Web Console, click AdministrationCluster SettingsCluster Operators to view cluster operators.
  • A storage class with provisioner openshift-storage.rbd.csi.ceph.com is available. In the OpenShift Web Console, click Storage → Storage Classes to view available storage classes.

Procedure

  1. In the OpenShift Web Console, go to WorkloadsConfig Maps.
  2. Set the Project dropdown to openshift-monitoring.
  3. Click Create Config Map.
  4. Define a new cluster-monitoring-config Config Map using the following example.

    Replace the content in angle brackets (<, >) with your own values, for example, retention: 24h or storage: 40Gi.

    Replace the storageClassName with the storageclass that uses the provisioner openshift-storage.rbd.csi.ceph.com. In the example given below the name of the storageclass is ocs-storagecluster-ceph-rbd.

    Example cluster-monitoring-config Config Map

    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: cluster-monitoring-config
      namespace: openshift-monitoring
    data:
      config.yaml: |
          prometheusK8s:
            retention: <time to retain monitoring files, e.g. 24h>
            volumeClaimTemplate:
              metadata:
                name: ocs-prometheus-claim
              spec:
                storageClassName: ocs-storagecluster-ceph-rbd
                resources:
                  requests:
                    storage: <size of claim, e.g. 40Gi>
          alertmanagerMain:
            volumeClaimTemplate:
              metadata:
                name: ocs-alertmanager-claim
              spec:
                storageClassName: ocs-storagecluster-ceph-rbd
                resources:
                  requests:
                    storage: <size of claim, e.g. 40Gi>

  5. Click Create to save and create the Config Map.

Verification steps

  1. Verify that the Persistent Volume Claims are bound to the pods.

    1. Go to StoragePersistent Volume Claims.
    2. Set the Project dropdown to openshift-monitoring.
    3. Verify that 5 Persistent Volume Claims are visible with a state of Bound, attached to three alertmanager-main-* pods, and two prometheus-k8s-* pods.

      Monitoring storage created and bound

      Screenshot of OpenShift Web Console showing five pods with persistent volume claims bound in the openshift-monitoring project

  2. Verify that the new alertmanager-main-* pods appear with a state of Running.

    1. Go to WorkloadsPods.
    2. Click the new alertmanager-main-* pods to view the pod details.
    3. Scroll down to Volumes and verify that the volume has a Type, ocs-alertmanager-claim that matches one of your new Persistent Volume Claims, for example, ocs-alertmanager-claim-alertmanager-main-0.

      Persistent Volume Claims attached to alertmanager-main-* pod

      Screenshot of OpenShift Web Console showing persistent volume claim attached to the altermanager pod

  3. Verify that the new prometheus-k8s-* pods appear with a state of Running.

    1. Click the new prometheus-k8s-* pods to view the pod details.
    2. Scroll down to Volumes and verify that the volume has a Type, ocs-prometheus-claim that matches one of your new Persistent Volume Claims, for example, ocs-prometheus-claim-prometheus-k8s-0.

      Persistent Volume Claims attached to prometheus-k8s-* pod

      Screenshot of OpenShift Web Console showing persistent volume claim attached to the prometheus pod

6.3. Cluster logging for OpenShift Container Storage

You can deploy cluster logging to aggregate logs for a range of OpenShift Container Platform services. For information about how to deploy cluster logging, see Deploying cluster logging.

Upon initial OpenShift Container Platform deployment, OpenShift Container Storage is not configured by default and the OpenShift Container Platform cluster will solely rely on default storage available from the nodes. You can edit the default configuration of OpenShift logging (ElasticSearch) to be backed by OpenShift Container Storage to have OpenShift Container Storage backed logging (Elasticsearch).

Important

Always ensure that you have plenty of storage capacity for these services. If you run out of storage space for these critical services, the logging application becomes inoperable and very difficult to recover.

Red Hat recommends configuring shorter curation and retention intervals for these services. See Cluster logging curator in the OpenShift Container Platform documentation for details.

If you run out of storage space for these services, contact Red Hat Customer Support.

6.3.1. Configuring persistent storage

You can configure a persistent storage class and size for the Elasticsearch cluster using the storage class name and size parameters. The Cluster Logging Operator creates a Persistent Volume Claim for each data node in the Elasticsearch cluster based on these parameters. For example:

spec:
    logStore:
      type: "elasticsearch"
      elasticsearch:
        nodeCount: 3
        storage:
          storageClassName: "ocs-storagecluster-ceph-rbd”
          size: "200G"

This example specifies that each data node in the cluster will be bound to a Persistent Volume Claim that requests 200GiB of ocs-storagecluster-ceph-rbd storage. Each primary shard will be backed by a single replica. A copy of the shard is replicated across all the nodes and are always available and the copy can be recovered if at least two nodes exist due to the single redundancy policy. For information about Elasticsearch replication policies, see Elasticsearch replication policy in About deploying and configuring cluster logging.

Note

Omission of the storage block will result in a deployment backed by default storage. For example:

spec:
    logStore:
      type: "elasticsearch"
      elasticsearch:
        nodeCount: 3
        storage: {}

For more information, see Configuring cluster logging.

6.3.2. Configuring cluster logging to use OpenShift Container Storage

Follow the instructions in this section to configure OpenShift Container Storage as storage for the OpenShift cluster logging.

Note

You can obtain all the logs when you configure logging for the first time in OpenShift Container Storage. However, after you uninstall and reinstall logging, the old logs are removed and only the new logs are processed.

Prerequisites

  • You have administrative access to OpenShift Web Console.
  • OpenShift Container Storage Operator is installed and running in the openshift-storage namespace.
  • Cluster logging Operator is installed and running in the openshift-logging namespace.

Procedure

  1. Click Administration → Custom Resource Definitions from the left pane of the OpenShift Web Console.
  2. On the Custom Resource Definitions page, click ClusterLogging.
  3. On the Custom Resource Definition Overview page, select View Instances from the Actions menu or click the Instances Tab.
  4. On the Cluster Logging page, click Create Cluster Logging.

    You might have to refresh the page to load the data.

  5. In the YAML, replace the storageClassName with the storageclass that uses the provisioner openshift-storage.rbd.csi.ceph.com. In the example given below the name of the storageclass is ocs-storagecluster-ceph-rbd:

    apiVersion: "logging.openshift.io/v1"
    kind: "ClusterLogging"
    metadata:
      name: "instance"
      namespace: "openshift-logging"
    spec:
      managementState: "Managed"
      logStore:
        type: "elasticsearch"
        elasticsearch:
          nodeCount: 3
          storage:
            storageClassName: ocs-storagecluster-ceph-rbd
            size: 200G # Change as per your requirement
          redundancyPolicy: "SingleRedundancy"
      visualization:
        type: "kibana"
        kibana:
          replicas: 1
      curation:
        type: "curator"
        curator:
          schedule: "30 3 * * *"
      collection:
        logs:
          type: "fluentd"
          fluentd: {}

    If you have tainted the OpenShift Container Storage nodes, you must add toleration to enable scheduling of the daemonset pods for logging.

    spec:
    [...]
      collection:
        logs:
          fluentd:
            tolerations:
            - effect: NoSchedule
              key: node.ocs.openshift.io/storage
              value: 'true'
          type: fluentd
  6. Click Save.

Verification steps

  1. Verify that the Persistent Volume Claims are bound to the elasticsearch pods.

    1. Go to StoragePersistent Volume Claims.
    2. Set the Project dropdown to openshift-logging.
    3. Verify that Persistent Volume Claims are visible with a state of Bound, attached to elasticsearch-* pods.

      Figure 6.1. Cluster logging created and bound

      Screenshot of Persistent Volume Claims with a bound state attached to elasticsearch pods
  2. Verify that the new cluster logging is being used.

    1. Click Workload → Pods.
    2. Set the Project to openshift-logging.
    3. Verify that the new elasticsearch-* pods appear with a state of Running.
    4. Click the new elasticsearch-* pod to view pod details.
    5. Scroll down to Volumes and verify that the elasticsearch volume has a Type that matches your new Persistent Volume Claim, for example, elasticsearch-elasticsearch-cdm-9r624biv-3.
    6. Click the Persistent Volume Claim name and verify the storage class name in the PersistentVolumeClaim Overview page.
Note

Make sure to use a shorter curator time to avoid PV full scenario on PVs attached to Elasticsearch pods.

You can configure Curator to delete Elasticsearch data based on retention settings. It is recommended that you set the following default index data retention of 5 days as a default.

config.yaml: |
    openshift-storage:
      delete:
        days: 5

For more details, see Curation of Elasticsearch Data.

Note

To uninstall the cluster logging backed by Persistent Volume Claim, use the procedure removing the cluster logging operator from OpenShift Container Storage in the uninstall chapter of the respective deployment guide.