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Chapter 5. Storage classes and storage pools

The OpenShift Data Foundation operator installs a default storage class depending on the platform in use. This default storage class is owned and controlled by the operator and it cannot be deleted or modified. However, you can create a custom storage class if you want the storage class to have a different behaviour.

You can create multiple storage pools which map to storage classes that provide the following features:

  • Enable applications with their own high availability to use persistent volumes with two replicas, potentially improving application performance.
  • Save space for persistent volume claims using storage classes with compression enabled.
Note

Multiple storage classes and multiple pools are not supported for external mode OpenShift Data Foundation clusters.

Note

With a minimal cluster of a single device set, only two new storage classes can be created. Every storage cluster expansion allows two new additional storage classes.

5.1. Creating storage classes and pools

You can create a storage class using an existing pool or you can create a new pool for the storage class while creating it.

Prerequisites

  • Ensure that you are logged into the OpenShift Container Platform web console and OpenShift Data Foundation cluster is in Ready state.

Procedure

  1. Click StorageStorageClasses.
  2. Click Create Storage Class.
  3. Enter the storage class Name and Description.
  4. Reclaim Policy is set to Delete as the default option. Use this setting.

    If you change the reclaim policy to Retain in the storage class, the persistent volume (PV) remains in Released state even after deleting the persistent volume claim (PVC).

  5. Volume binding mode is set to WaitForConsumer as the default option.

    If you choose the Immediate option, then the PV gets created immediately when creating the PVC.

  6. Select RBD Provisioner which is the plugin used for provisioning the persistent volumes.
  7. Select an existing Storage Pool from the list or create a new pool.

    Create new pool
    1. Click Create New Pool.
    2. Enter Pool name.
    3. Choose 2-way-Replication or 3-way-Replication as the Data Protection Policy.
    4. Select Enable compression if you need to compress the data.

      Enabling compression can impact application performance and might prove ineffective when data to be written is already compressed or encrypted. Data written before enabling compression will not be compressed.

    5. Click Create to create the new storage pool.
    6. Click Finish after the pool is created.
  8. Optional: Select Enable Encryption checkbox.
  9. Click Create to create the storage class.

5.2. Creating a storage class for persistent volume encryption

Prerequisites

Based on your use case, you must ensure to configure access to KMS for one of the following:

Procedure

  1. In the OpenShift Web Console, navigate to StorageStorageClasses.
  2. Click Create Storage Class.
  3. Enter the storage class Name and Description.
  4. Select either Delete or Retain for the Reclaim Policy. By default, Delete is selected.
  5. Select either Immediate or WaitForFirstConsumer as the Volume binding mode. WaitForConsumer is set as the default option.
  6. Select RBD Provisioner openshift-storage.rbd.csi.ceph.com which is the plugin used for provisioning the persistent volumes.
  7. Select Storage Pool where the volume data is stored from the list or create a new pool.
  8. Select the Enable encryption checkbox. There are two options available to set the KMS connection details:

    • Select existing KMS connection: Select an existing KMS connection from the drop-down list. The list is populated from the the connection details available in the csi-kms-connection-details ConfigMap.
    • Create new KMS connection: This is applicable for vaulttokens only.

      1. Key Management Service Provider is set to Vault by default.
      2. Enter a unique Connection Name, host Address of the Vault server ('https://<hostname or ip>'), Port number and Token.
      3. Expand Advanced Settings to enter additional settings and certificate details based on your Vault configuration:

        1. Enter the Key Value secret path in Backend Path that is dedicated and unique to OpenShift Data Foundation.
        2. Optional: Enter TLS Server Name and Vault Enterprise Namespace.
        3. Upload the respective PEM encoded certificate file to provide the CA Certificate, Client Certificate and Client Private Key .
        4. Click Save.
      4. Click Save.
  9. Click Create.
  10. Edit the ConfigMap to add the vaultBackend parameter if the HashiCorp Vault setup does not allow automatic detection of the Key/Value (KV) secret engine API version used by the backend path.

    Note

    vaultBackend is an optional parameters that is added to the configmap to specify the version of the KV secret engine API associated with the backend path. Ensure that the value matches the KV secret engine API version that is set for the backend path, otherwise it might result in a failure during persistent volume claim (PVC) creation.

    1. Identify the encryptionKMSID being used by the newly created storage class.

      1. On the OpenShift Web Console, navigate to StorageStorage Classes.
      2. Click the Storage class name → YAML tab.
      3. Capture the encryptionKMSID being used by the storage class.

        Example:

        encryptionKMSID: 1-vault
    2. On the OpenShift Web Console, navigate to WorkloadsConfigMaps.
    3. To view the KMS connection details, click csi-kms-connection-details.
    4. Edit the ConfigMap.

      1. Click Action menu (⋮)Edit ConfigMap.
      2. Add the vaultBackend parameter depending on the backend that is configured for the previously identified encryptionKMSID.

        You can assign kv for KV secret engine API, version 1 and kv-v2 for KV secret engine API, version 2.

        Example:

         kind: ConfigMap
         apiVersion: v1
         metadata:
           name: csi-kms-connection-details
         [...]
         data:
           1-vault: |-
             {
               "encryptionKMSType": "vaulttokens",
               "kmsServiceName": "1-vault",
               [...]
               "vaultBackend": "kv-v2"
             }
           2-vault: |-
             {
               "encryptionKMSType": "vaulttenantsa",
               [...]
               "vaultBackend": "kv"
             }
      3. Click Save

Next steps

  • The storage class can be used to create encrypted persistent volumes. For more information, see managing persistent volume claims.

    Important

    Red Hat works with the technology partners to provide this documentation as a service to the customers. However, Red Hat does not provide support for the HashiCorp product. For technical assistance with this product, contact HashiCorp.