Chapter 7. Post-installation storage configuration After installing OpenShift Container Platform, you can further expand and customize your cluster to your requirements, including storage configuration. 7.1. Dynamic provisioning 7.1.1. 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 detailed knowledge about the underlying storage volume sources. The OpenShift Container Platform 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 Platform. 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. 7.1.2. Available dynamic provisioning plug-ins OpenShift Container Platform 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 Red Hat OpenStack Platform (RHOSP) Cinder kubernetes.io/cinder RHOSP Manila Container Storage Interface (CSI) manila.csi.openstack.org Once installed, the OpenStack Manila CSI Driver Operator and ManilaDriver automatically create the required storage classes for all available Manila share types needed for dynamic provisioning. 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. Azure Disk kubernetes.io/azure-disk Azure File kubernetes.io/azure-file The persistent-volume-binder service account 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 Platform 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. 7.2. Defining a storage class StorageClass objects are currently a globally scoped object and must be created by cluster-admin or storage-admin users. Important The Cluster Storage Operator might install a default storage class depending on the platform in use. This storage class is owned and controlled by the operator. It cannot be deleted or modified beyond defining annotations and labels. If different behavior is desired, you must define a custom storage class. The following sections describe the basic definition for a StorageClass object and specific examples for each of the supported plug-in types. 7.2.1. Basic StorageClass object definition The following resource shows the parameters and default values that you use to configure a storage class. This example uses the AWS ElasticBlockStore (EBS) object definition. Sample StorageClass definition kind: StorageClass 1 apiVersion: storage.k8s.io/v1 2 metadata: name: gp2 3 annotations: 4 storageclass.kubernetes.io/is-default-class: 'true' ... provisioner: kubernetes.io/aws-ebs 5 parameters: 6 type: gp2 ... 1 (required) The API object type. 2 (required) The current apiVersion. 3 (required) The name of the storage class. 4 (optional) Annotations for the storage class. 5 (required) The type of provisioner associated with this storage class. 6 (optional) The parameters required for the specific provisioner, this will change from plug-in to plug-in. 7.2.2. Storage class annotations To set a storage class as the cluster-wide default, add the following annotation to your storage class metadata: storageclass.kubernetes.io/is-default-class: "true" For example: apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: storageclass.kubernetes.io/is-default-class: "true" ... This enables any persistent volume claim (PVC) that does not specify a specific storage class to automatically be provisioned through the default storage class. However, your cluster can have more than one storage class, but only one of them can be the default storage class. Note The beta annotation storageclass.beta.kubernetes.io/is-default-class is still working; however, it will be removed in a future release. To set a storage class description, add the following annotation to your storage class metadata: kubernetes.io/description: My Storage Class Description For example: apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: kubernetes.io/description: My Storage Class Description ... 7.2.3. RHOSP Cinder object definition cinder-storageclass.yaml kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: gold provisioner: kubernetes.io/cinder parameters: type: fast 1 availability: nova 2 fsType: ext4 3 1 Volume type created in Cinder. Default is empty. 2 Availability Zone. If not specified, volumes are generally round-robined across all active zones where the OpenShift Container Platform cluster has a node. 3 File system that is created on dynamically provisioned volumes. This value is copied to the fsType field of dynamically provisioned persistent volumes and the file system is created when the volume is mounted for the first time. The default value is ext4 . 7.2.4. AWS Elastic Block Store (EBS) object definition aws-ebs-storageclass.yaml kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: slow provisioner: kubernetes.io/aws-ebs parameters: type: io1 1 iopsPerGB: "10" 2 encrypted: "true" 3 kmsKeyId: keyvalue 4 fsType: ext4 5 1 (required) Select from io1 , gp2 , sc1 , st1 . The default is gp2 . See the AWS documentation for valid Amazon Resource Name (ARN) values. 2 (optional) Only for io1 volumes. I/O operations per second per GiB. The AWS volume plug-in multiplies this with the size of the requested volume to compute IOPS of the volume. The value cap is 20,000 IOPS, which is the maximum supported by AWS. See the AWS documentation for further details. 3 (optional) Denotes whether to encrypt the EBS volume. Valid values are true or false . 4 (optional) The full ARN of the key to use when encrypting the volume. If none is supplied, but encypted is set to true , then AWS generates a key. See the AWS documentation for a valid ARN value. 5 (optional) File system that is created on dynamically provisioned volumes. This value is copied to the fsType field of dynamically provisioned persistent volumes and the file system is created when the volume is mounted for the first time. The default value is ext4 . 7.2.5. Azure Disk object definition azure-advanced-disk-storageclass.yaml apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: managed-premium provisioner: kubernetes.io/azure-disk volumeBindingMode: WaitForFirstConsumer 1 allowVolumeExpansion: true parameters: kind: Managed 2 storageaccounttype: Premium_LRS 3 reclaimPolicy: Delete 1 Using WaitForFirstConsumer is strongly recommended. This provisions the volume while allowing enough storage to schedule the pod on a free worker node from an available zone. 2 Possible values are Shared (default), Managed , and Dedicated . Important Red Hat only supports the use of kind: Managed in the storage class. With Shared and Dedicated , Azure creates unmanaged disks, while OpenShift Container Platform creates a managed disk for machine OS (root) disks. But because Azure Disk does not allow the use of both managed and unmanaged disks on a node, unmanaged disks created with Shared or Dedicated cannot be attached to OpenShift Container Platform nodes. 3 Azure storage account SKU tier. Default is empty. Note that Premium VMs can attach both Standard_LRS and Premium_LRS disks, Standard VMs can only attach Standard_LRS disks, Managed VMs can only attach managed disks, and unmanaged VMs can only attach unmanaged disks. If kind is set to Shared , Azure creates all unmanaged disks in a few shared storage accounts in the same resource group as the cluster. If kind is set to Managed , Azure creates new managed disks. If kind is set to Dedicated and a storageAccount is specified, Azure uses the specified storage account for the new unmanaged disk in the same resource group as the cluster. For this to work: The specified storage account must be in the same region. Azure Cloud Provider must have write access to the storage account. If kind is set to Dedicated and a storageAccount is not specified, Azure creates a new dedicated storage account for the new unmanaged disk in the same resource group as the cluster. 7.2.6. Azure File object definition The Azure File storage class uses secrets to store the Azure storage account name and the storage account key that are required to create an Azure Files share. These permissions are created as part of the following procedure. Procedure Define a ClusterRole object that allows access to create and view secrets: apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: # name: system:azure-cloud-provider name: <persistent-volume-binder-role> 1 rules: - apiGroups: [''] resources: ['secrets'] verbs: ['get','create'] 1 The name of the cluster role to view and create secrets. Add the cluster role to the service account: USD oc adm policy add-cluster-role-to-user <persistent-volume-binder-role> Example output system:serviceaccount:kube-system:persistent-volume-binder Create the Azure File StorageClass object: kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: <azure-file> 1 provisioner: kubernetes.io/azure-file parameters: location: eastus 2 skuName: Standard_LRS 3 storageAccount: <storage-account> 4 reclaimPolicy: Delete volumeBindingMode: Immediate 1 Name of the storage class. The persistent volume claim uses this storage class for provisioning the associated persistent volumes. 2 Location of the Azure storage account, such as eastus . Default is empty, meaning that a new Azure storage account will be created in the OpenShift Container Platform cluster's location. 3 SKU tier of the Azure storage account, such as Standard_LRS . Default is empty, meaning that a new Azure storage account will be created with the Standard_LRS SKU. 4 Name of the Azure storage account. If a storage account is provided, then skuName and location are ignored. If no storage account is provided, then the storage class searches for any storage account that is associated with the resource group for any accounts that match the defined skuName and location . 7.2.6.1. Considerations when using Azure File The following file system features are not supported by the default Azure File storage class: Symlinks Hard links Extended attributes Sparse files Named pipes Additionally, the owner user identifier (UID) of the Azure File mounted directory is different from the process UID of the container. The uid mount option can be specified in the StorageClass object to define a specific user identifier to use for the mounted directory. The following StorageClass object demonstrates modifying the user and group identifier, along with enabling symlinks for the mounted directory. kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: azure-file mountOptions: - uid=1500 1 - gid=1500 2 - mfsymlinks 3 provisioner: kubernetes.io/azure-file parameters: location: eastus skuName: Standard_LRS reclaimPolicy: Delete volumeBindingMode: Immediate 1 Specifies the user identifier to use for the mounted directory. 2 Specifies the group identifier to use for the mounted directory. 3 Enables symlinks. 7.2.7. GCE PersistentDisk (gcePD) object definition gce-pd-storageclass.yaml apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: standard provisioner: kubernetes.io/gce-pd parameters: type: pd-standard 1 replication-type: none volumeBindingMode: WaitForFirstConsumer allowVolumeExpansion: true reclaimPolicy: Delete 1 Select either pd-standard or pd-ssd . The default is pd-standard . 7.2.8. VMware vSphere object definition vsphere-storageclass.yaml kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: slow provisioner: kubernetes.io/vsphere-volume 1 parameters: diskformat: thin 2 1 For more information about using VMware vSphere with OpenShift Container Platform, see the VMware vSphere documentation . 2 diskformat : thin , zeroedthick and eagerzeroedthick are all valid disk formats. See vSphere docs for additional details regarding the disk format types. The default value is thin . 7.3. Changing the default storage class If you are using AWS, use the following process to change the default storage class. This process assumes you have two storage classes defined, gp2 and standard , and you want to change the default storage class from gp2 to standard . List the storage class: USD oc get storageclass Example output NAME TYPE gp2 (default) kubernetes.io/aws-ebs 1 standard kubernetes.io/aws-ebs 1 (default) denotes the default storage class. Change the value of the annotation storageclass.kubernetes.io/is-default-class to false for the default storage class: USD oc patch storageclass gp2 -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "false"}}}' Make another storage class the default by adding or modifying the annotation as storageclass.kubernetes.io/is-default-class=true . USD oc patch storageclass standard -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "true"}}}' Verify the changes: USD oc get storageclass Example output NAME TYPE gp2 kubernetes.io/aws-ebs standard (default) kubernetes.io/aws-ebs 7.4. Optimizing storage Optimizing storage helps to minimize storage use across all resources. By optimizing storage, administrators help ensure that existing storage resources are working in an efficient manner. 7.5. Available persistent storage options Understand your persistent storage options so that you can optimize your OpenShift Container Platform environment. Table 7.1. Available storage options Storage type Description Examples Block Presented to the operating system (OS) as a block device Suitable for applications that need full control of storage and operate at a low level on files bypassing the file system Also referred to as a Storage Area Network (SAN) Non-shareable, which means that only one client at a time can mount an endpoint of this type AWS EBS and VMware vSphere support dynamic persistent volume (PV) provisioning natively in OpenShift Container Platform. File Presented to the OS as a file system export to be mounted Also referred to as Network Attached Storage (NAS) Concurrency, latency, file locking mechanisms, and other capabilities vary widely between protocols, implementations, vendors, and scales. RHEL NFS, NetApp NFS [1] , and Vendor NFS Object Accessible through a REST API endpoint Configurable for use in the OpenShift Container Platform Registry Applications must build their drivers into the application and/or container. AWS S3 NetApp NFS supports dynamic PV provisioning when using the Trident plug-in. Important Currently, CNS is not supported in OpenShift Container Platform 4.7. 7.6. Recommended configurable storage technology The following table summarizes the recommended and configurable storage technologies for the given OpenShift Container Platform cluster application. Table 7.2. Recommended and configurable storage technology Storage type ROX 1 RWX 2 Registry Scaled registry Metrics 3 Logging Apps 1 ReadOnlyMany 2 ReadWriteMany 3 Prometheus is the underlying technology used for metrics. 4 This does not apply to physical disk, VM physical disk, VMDK, loopback over NFS, AWS EBS, and Azure Disk. 5 For metrics, using file storage with the ReadWriteMany (RWX) access mode is unreliable. If you use file storage, do not configure the RWX access mode on any persistent volume claims (PVCs) that are configured for use with metrics. 6 For logging, using any shared storage would be an anti-pattern. One volume per elasticsearch is required. 7 Object storage is not consumed through OpenShift Container Platform's PVs or PVCs. Apps must integrate with the object storage REST API. Block Yes 4 No Configurable Not configurable Recommended Recommended Recommended File Yes 4 Yes Configurable Configurable Configurable 5 Configurable 6 Recommended Object Yes Yes Recommended Recommended Not configurable Not configurable Not configurable 7 Note A scaled registry is an OpenShift Container Platform registry where two or more pod replicas are running. 7.6.1. Specific application storage recommendations Important Testing shows issues with using the NFS server on Red Hat Enterprise Linux (RHEL) as storage backend for core services. This includes the OpenShift Container Registry and Quay, Prometheus for monitoring storage, and Elasticsearch for logging storage. Therefore, using RHEL NFS to back PVs used by core services is not recommended. Other NFS implementations on the marketplace might not have these issues. Contact the individual NFS implementation vendor for more information on any testing that was possibly completed against these OpenShift Container Platform core components. 7.6.1.1. Registry In a non-scaled/high-availability (HA) OpenShift Container Platform registry cluster deployment: The storage technology does not have to support RWX access mode. The storage technology must ensure read-after-write consistency. The preferred storage technology is object storage followed by block storage. File storage is not recommended for OpenShift Container Platform registry cluster deployment with production workloads. 7.6.1.2. Scaled registry In a scaled/HA OpenShift Container Platform registry cluster deployment: The storage technology must support RWX access mode. The storage technology must ensure read-after-write consistency. The preferred storage technology is object storage. Amazon Simple Storage Service (Amazon S3), Google Cloud Storage (GCS), Microsoft Azure Blob Storage, and OpenStack Swift are supported. Object storage should be S3 or Swift compliant. For non-cloud platforms, such as vSphere and bare metal installations, the only configurable technology is file storage. Block storage is not configurable. 7.6.1.3. Metrics In an OpenShift Container Platform hosted metrics cluster deployment: The preferred storage technology is block storage. Object storage is not configurable. Important It is not recommended to use file storage for a hosted metrics cluster deployment with production workloads. 7.6.1.4. Logging In an OpenShift Container Platform hosted logging cluster deployment: The preferred storage technology is block storage. Object storage is not configurable. 7.6.1.5. Applications Application use cases vary from application to application, as described in the following examples: Storage technologies that support dynamic PV provisioning have low mount time latencies, and are not tied to nodes to support a healthy cluster. Application developers are responsible for knowing and understanding the storage requirements for their application, and how it works with the provided storage to ensure that issues do not occur when an application scales or interacts with the storage layer. 7.6.2. Other specific application storage recommendations Important It is not recommended to use RAID configurations on Write intensive workloads, such as etcd . If you are running etcd with a RAID configuration, you might be at risk of encountering performance issues with your workloads. Red Hat OpenStack Platform (RHOSP) Cinder: RHOSP Cinder tends to be adept in ROX access mode use cases. Databases: Databases (RDBMSs, NoSQL DBs, etc.) tend to perform best with dedicated block storage. The etcd database must have enough storage and adequate performance capacity to enable a large cluster. Information about monitoring and benchmarking tools to establish ample storage and a high-performance environment is described in Recommended etcd practices . Additional resources Recommended etcd practices 7.7. Deploy Red Hat OpenShift Container Storage Red Hat OpenShift Container Storage is a provider of agnostic persistent storage for OpenShift Container Platform supporting file, block, and object storage, either in-house or in hybrid clouds. As a Red Hat storage solution, Red Hat OpenShift Container Storage is completely integrated with OpenShift Container Platform for deployment, management, and monitoring. If you are looking for Red Hat OpenShift Container Storage information about... See the following Red Hat OpenShift Container Storage documentation: What's new, known issues, notable bug fixes, and Technology Previews OpenShift Container Storage 4.7 Release Notes Supported workloads, layouts, hardware and software requirements, sizing and scaling recommendations Planning your OpenShift Container Storage 4.5 deployment Instructions on preparing to deploy when your environment is not directly connected to the internet Preparing to deploy OpenShift Container Storage 4.5 in a disconnected environment Instructions on deploying OpenShift Container Storage to use an external Red Hat Ceph Storage cluster Deploying OpenShift Container Storage 4.5 in external mode Instructions on deploying OpenShift Container Storage to local storage on bare metal infrastructure Deploying OpenShift Container Storage 4.5 using bare metal infrastructure Instructions on deploying OpenShift Container Storage on Red Hat OpenShift Container Platform VMware vSphere clusters Deploying OpenShift Container Storage 4.5 on VMware vSphere Instructions on deploying OpenShift Container Storage using Amazon Web Services for local or cloud storage Deploying OpenShift Container Storage 4.5 using Amazon Web Services Instructions on deploying and managing OpenShift Container Storage on existing Red Hat OpenShift Container Platform Google Cloud clusters Deploying and managing OpenShift Container Storage 4.5 using Google Cloud Instructions on deploying and managing OpenShift Container Storage on existing Red Hat OpenShift Container Platform Azure clusters Deploying and managing OpenShift Container Storage 4.5 using Microsoft Azure Managing a Red Hat OpenShift Container Storage 4.5 cluster Managing OpenShift Container Storage 4.5 Monitoring a Red Hat OpenShift Container Storage 4.5 cluster Monitoring Red Hat OpenShift Container Storage 4.5 Resolve issues encountered during operations Troubleshooting OpenShift Container Storage 4.5 Migrating your OpenShift Container Platform cluster from version 3 to version 4 Migration

Commands:
kind: StorageClass 1 apiVersion: storage.k8s.io/v1 2 metadata: name: gp2 3 annotations: 4 storageclass.kubernetes.io/is-default-class: 'true' provisioner: kubernetes.io/aws-ebs 5 parameters: 6 type: gp2
storageclass.kubernetes.io/is-default-class: "true"
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: storageclass.kubernetes.io/is-default-class: "true"
kubernetes.io/description: My Storage Class Description
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: kubernetes.io/description: My Storage Class Description
kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: gold provisioner: kubernetes.io/cinder parameters: type: fast 1 availability: nova 2 fsType: ext4 3
kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: slow provisioner: kubernetes.io/aws-ebs parameters: type: io1 1 iopsPerGB: "10" 2 encrypted: "true" 3 kmsKeyId: keyvalue 4 fsType: ext4 5
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: managed-premium provisioner: kubernetes.io/azure-disk volumeBindingMode: WaitForFirstConsumer 1 allowVolumeExpansion: true parameters: kind: Managed 2 storageaccounttype: Premium_LRS 3 reclaimPolicy: Delete
apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: system:azure-cloud-provider name: <persistent-volume-binder-role> 1 rules: - apiGroups: [''] resources: ['secrets'] verbs: ['get','create']
oc adm policy add-cluster-role-to-user <persistent-volume-binder-role>
system:serviceaccount:kube-system:persistent-volume-binder
kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: <azure-file> 1 provisioner: kubernetes.io/azure-file parameters: location: eastus 2 skuName: Standard_LRS 3 storageAccount: <storage-account> 4 reclaimPolicy: Delete volumeBindingMode: Immediate
kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: azure-file mountOptions: - uid=1500 1 - gid=1500 2 - mfsymlinks 3 provisioner: kubernetes.io/azure-file parameters: location: eastus skuName: Standard_LRS reclaimPolicy: Delete volumeBindingMode: Immediate
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: standard provisioner: kubernetes.io/gce-pd parameters: type: pd-standard 1 replication-type: none volumeBindingMode: WaitForFirstConsumer allowVolumeExpansion: true reclaimPolicy: Delete
kind: StorageClass apiVersion: storage.k8s.io/v1 metadata: name: slow provisioner: kubernetes.io/vsphere-volume 1 parameters: diskformat: thin 2
oc get storageclass
NAME TYPE gp2 (default) kubernetes.io/aws-ebs 1 standard kubernetes.io/aws-ebs
oc patch storageclass gp2 -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "false"}}}'
oc patch storageclass standard -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "true"}}}'
oc get storageclass
NAME TYPE gp2 kubernetes.io/aws-ebs standard (default) kubernetes.io/aws-ebs