Chapter 6. Post-installation storage configuration
After installing OpenShift Container Platform, you can further expand and customize your cluster to your requirements, including storage configuration.
6.1. Dynamic provisioning
6.1.1. 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.
6.1.2. 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 |
| |
| RHOSP Manila Container Storage Interface (CSI) |
| 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) |
|
For dynamic provisioning when using multiple clusters in different zones, tag each node with |
| Azure Disk |
| |
| Azure File |
|
The |
| GCE Persistent Disk (gcePD) |
| 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. |
|
|
Any chosen provisioner plug-in also requires configuration for the relevant cloud, host, or third-party provider as per the relevant documentation.
6.2. Defining a storage class
StorageClass objects are currently a globally scoped object and must be created by cluster-admin or storage-admin users.
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.
6.2.1. 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.
6.2.2. 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.
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
...6.2.3. 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
fsTypefield of dynamically provisioned persistent volumes and the file system is created when the volume is mounted for the first time. The default value isext4.
6.2.4. 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 isgp2. 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
trueorfalse. - 4
- (optional) The full ARN of the key to use when encrypting the volume. If none is supplied, but
encyptedis set totrue, 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
fsTypefield of dynamically provisioned persistent volumes and the file system is created when the volume is mounted for the first time. The default value isext4.
6.2.5. 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
WaitForFirstConsumeris 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, andDedicated.ImportantRed Hat only supports the use of
kind: Managedin the storage class.With
SharedandDedicated, 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 withSharedorDedicatedcannot be attached to OpenShift Container Platform nodes. - 3
- Azure storage account SKU tier. Default is empty. Note that Premium VMs can attach both
Standard_LRSandPremium_LRSdisks, Standard VMs can only attachStandard_LRSdisks, Managed VMs can only attach managed disks, and unmanaged VMs can only attach unmanaged disks.-
If
kindis set toShared, Azure creates all unmanaged disks in a few shared storage accounts in the same resource group as the cluster. -
If
kindis set toManaged, Azure creates new managed disks. If
kindis set toDedicatedand astorageAccountis 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
kindis set toDedicatedand astorageAccountis not specified, Azure creates a new dedicated storage account for the new unmanaged disk in the same resource group as the cluster.
-
If
6.2.6. 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
ClusterRoleobject 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:
$ 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
StorageClassobject: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 theStandard_LRSSKU. - 4
- Name of the Azure storage account. If a storage account is provided, then
skuNameandlocationare 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 definedskuNameandlocation.
6.2.6.1. 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
6.2.7. 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-standardorpd-ssd. The default ispd-standard.
6.2.8. 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,zeroedthickandeagerzeroedthickare all valid disk formats. See vSphere docs for additional details regarding the disk format types. The default value isthin.
6.3. 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:
$ 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-classtofalsefor the default storage class:$ 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.$ oc patch storageclass standard -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "true"}}}'Verify the changes:
$ oc get storageclass
Example output
NAME TYPE gp2 kubernetes.io/aws-ebs standard (default) kubernetes.io/aws-ebs
6.4. 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.
6.5. Available persistent storage options
Understand your persistent storage options so that you can optimize your OpenShift Container Platform environment.
| Storage type | Description | Examples |
|---|---|---|
| Block |
| AWS EBS and VMware vSphere support dynamic persistent volume (PV) provisioning natively in OpenShift Container Platform. |
| File |
| RHEL NFS, NetApp NFS [1], and Vendor NFS |
| Object |
| AWS S3 |
- NetApp NFS supports dynamic PV provisioning when using the Trident plug-in.
Currently, CNS is not supported in OpenShift Container Platform 4.6.
6.6. Recommended configurable storage technology
The following table summarizes the recommended and configurable storage technologies for the given OpenShift Container Platform cluster application.
| Storage type | ROX1 | RWX2 | Registry | Scaled registry | Metrics3 | Logging | Apps |
|---|---|---|---|---|---|---|---|
|
1
2 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 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 | Yes4 | No | Configurable | Not configurable | Recommended | Recommended | Recommended |
| File | Yes4 | Yes | Configurable | Configurable | Configurable5 | Configurable6 | Recommended |
| Object | Yes | Yes | Recommended | Recommended | Not configurable | Not configurable | Not configurable7 |
A scaled registry is an OpenShift Container Platform registry where two or more pod replicas are running.
6.6.1. Specific application storage recommendations
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.
6.6.1.1. 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.
6.6.1.2. 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.
6.6.1.3. Metrics
In an OpenShift Container Platform hosted metrics cluster deployment:
- The preferred storage technology is block storage.
- Object storage is not configurable.
It is not recommended to use file storage for a hosted metrics cluster deployment with production workloads.
6.6.1.4. Logging
In an OpenShift Container Platform hosted logging cluster deployment:
- The preferred storage technology is block storage.
- Object storage is not configurable.
6.6.1.5. 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.
6.6.2. Other specific application storage recommendations
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
6.7. 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 | |
| Supported workloads, layouts, hardware and software requirements, sizing and scaling recommendations | |
| 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 | |
| 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 | |
| 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 | |
| Monitoring a Red Hat OpenShift Container Storage 4.5 cluster | |
| Resolve issues encountered during operations | |
| Migrating your OpenShift Container Platform cluster from version 3 to version 4 |
