Chapter 9. Managing persistent volume claims
Chapter 9. Managing persistent volume claims 9.1. Configuring application pods to use OpenShift Container Storage Follow the instructions in this section to configure OpenShift Container Storage as storage for an application pod. 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 Operators Installed Operators to view installed operators. The default storage classes provided by OpenShift Container Storage are available. In OpenShift Web Console, click Storage Storage Classes to view default storage classes. Procedure Create a Persistent Volume Claim (PVC) for the application to use. In OpenShift Web Console, click Storage Persistent Volume Claims . Set the Project for the application pod. Click Create Persistent Volume Claim . Specify a Storage Class provided by OpenShift Container Storage. Specify the PVC Name , for example, myclaim . Select the required Access Mode . Specify a Size as per application requirement. Click Create and wait until the PVC is in Bound status. Configure a new or existing application pod to use the new PVC. For a new application pod, perform the following steps: Click Workloads -> Pods . Create a new application pod. Under the spec: section, add volume: section to add the new PVC as a volume for the application pod. For example: For an existing application pod, perform the following steps: Click Workloads -> Deployment Configs . Search for the required deployment config associated with the application pod. Click on its Action menu (...) Edit Deployment Config . Under the spec: section, add volume: section to add the new PVC as a volume for the application pod and click Save . For example: Verify that the new configuration is being used. Click Workloads Pods . Set the Project for the application pod. Verify that the application pod appears with a status of Running . Click the application pod name to view pod details. Scroll down to Volumes section and verify that the volume has a Type that matches your new Persistent Volume Claim, for example, myclaim . 9.2. Viewing Persistent Volume Claim request status Use this procedure to view the status of a PVC request. Prerequisites Administrator access to OpenShift Container Storage. Procedure Log in to OpenShift Web Console. Click Storage Persistent Volume Claims Search for the required PVC name by using the Filter textbox. You can also filter the list of PVCs by Name or Label to narrow down the list Check the Status column corresponding to the required PVC. Click the required Name to view the PVC details. 9.3. Reviewing Persistent Volume Claim request events Use this procedure to review and address Persistent Volume Claim (PVC) request events. Prerequisites Administrator access to OpenShift Web Console. Procedure Log in to OpenShift Web Console. Click Home Overview Persistent Storage Locate the Inventory card to see the number of PVCs with errors. Click Storage Persistent Volume Claims Search for the required PVC using the Filter textbox. Click on the PVC name and navigate to Events Address the events as required or as directed. 9.4. Expanding Persistent Volume Claims OpenShift Container Storage 4.6 introduces the ability to expand Persistent Volume Claims providing more flexibility in the management of persistent storage resources. Expansion is supported for the following Persistent Volumes: PVC with ReadWriteOnce (RWO) and ReadWriteMany (RWX) access that is based on Ceph File System (CephFS) for volume mode Filesystem . PVC with ReadWriteOnce (RWO) access that is based on Ceph RADOS Block Devices (RBDs) with volume mode Filesystem . PVC with ReadWriteOnce (RWO) access that is based on Ceph RADOS Block Devices (RBDs) with volume mode Block . Warning OSD and MON PVC expansion is not supported by Red Hat. Prerequisites Administrator access to OpenShift Web Console. Procedure In OpenShift Web Console, navigate to Storage Persistent Volume Claims . Click the Action Menu (...) to the Persistent Volume Claim you want to expand. Click Expand PVC : Select the new size of the Persistent Volume Claim, then click Expand : To verify the expansion, navigate to the PVC's details page and verify the Capacity field has the correct size requested. Note When expanding PVCs based on Ceph RADOS Block Devices (RBDs), if the PVC is not already attached to a pod the Condition type is FileSystemResizePending in the PVC's details page. Once the volume is mounted, filesystem resize succeeds and the new size is reflected in the Capacity field. 9.5. Dynamic provisioning 9.5.1. About dynamic provisioning The StorageClass resource object describes and classifies storage that can be requested, as well as provides a means for passing parameters for dynamically provisioned storage on demand. StorageClass objects can also serve as a management mechanism for controlling different levels of storage and access to the storage. Cluster Administrators ( cluster-admin ) or Storage Administrators ( storage-admin ) define and create the StorageClass objects that users can request without needing any intimate knowledge about the underlying storage volume sources. The OpenShift Container Storage persistent volume framework enables this functionality and allows administrators to provision a cluster with persistent storage. The framework also gives users a way to request those resources without having any knowledge of the underlying infrastructure. Many storage types are available for use as persistent volumes in OpenShift Container Storage. While all of them can be statically provisioned by an administrator, some types of storage are created dynamically using the built-in provider and plug-in APIs. 9.5.2. Dynamic provisioning in OpenShift Container Storage Red Hat OpenShift Container Storage is software-defined storage that is optimised for container environments. It runs as an operator on OpenShift Container Platform to provide highly integrated and simplified persistent storage management for containers. OpenShift Container Storage supports a variety of storage types, including: Block storage for databases Shared file storage for continuous integration, messaging, and data aggregation Object storage for archival, backup, and media storage Version 4 uses Red Hat Ceph Storage to provide the file, block, and object storage that backs persistent volumes, and Rook.io to manage and orchestrate provisioning of persistent volumes and claims. NooBaa provides object storage, and its Multicloud Gateway allows object federation across multiple cloud environments (available as a Technology Preview). In OpenShift Container Storage 4, the Red Hat Ceph Storage Container Storage Interface (CSI) driver for RADOS Block Device (RBD) and Ceph File System (CephFS) handles the dynamic provisioning requests. When a PVC request comes in dynamically, the CSI driver has the following options: Create a PVC with ReadWriteOnce (RWO) and ReadWriteMany (RWX) access that is based on Ceph RBDs with volume mode Block Create a PVC with ReadWriteOnce (RWO) access that is based on Ceph RBDs with volume mode Filesystem Create a PVC with ReadWriteOnce (RWO) and ReadWriteMany (RWX) access that is based on CephFS for volume mode Filesystem The judgment of which driver (RBD or CephFS) to use is based on the entry in the storageclass.yaml file. 9.5.3. Available dynamic provisioning plug-ins OpenShift Container Storage provides the following provisioner plug-ins, which have generic implementations for dynamic provisioning that use the cluster's configured provider's API to create new storage resources: Storage type Provisioner plug-in name Notes OpenStack Cinder kubernetes.io/cinder AWS Elastic Block Store (EBS) kubernetes.io/aws-ebs For dynamic provisioning when using multiple clusters in different zones, tag each node with Key=kubernetes.io/cluster/<cluster_name>,Value=<cluster_id> where <cluster_name> and <cluster_id> are unique per cluster. AWS Elastic File System (EFS) Dynamic provisioning is accomplished through the EFS provisioner pod and not through a provisioner plug-in. Azure Disk kubernetes.io/azure-disk Azure File kubernetes.io/azure-file The persistent-volume-binder ServiceAccount requires permissions to create and get Secrets to store the Azure storage account and keys. GCE Persistent Disk (gcePD) kubernetes.io/gce-pd In multi-zone configurations, it is advisable to run one OpenShift Container Storage cluster per GCE project to avoid PVs from being created in zones where no node in the current cluster exists. VMware vSphere kubernetes.io/vsphere-volume Important Any chosen provisioner plug-in also requires configuration for the relevant cloud, host, or third-party provider as per the relevant documentation.
volumes: - name: <volume_name> persistentVolumeClaim: claimName: <pvc_name> volumes: - name: mypd persistentVolumeClaim: claimName: myclaim volumes: - name: <volume_name> persistentVolumeClaim: claimName: <pvc_name> volumes: - name: mypd persistentVolumeClaim: claimName: myclaim