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Azure Disk CSI Driver Operator

Overview

OKD is capable of provisioning persistent volumes (PVs) using the Container Storage Interface (CSI) driver for Microsoft Azure Disk Storage.

Familiarity with persistent storage and configuring CSI volumes is recommended when working with a CSI Operator and driver.

To create CSI-provisioned PVs that mount to Azure Disk storage assets, OKD installs the Azure Disk CSI Driver Operator and the Azure Disk CSI driver by default in the openshift-cluster-csi-drivers namespace.

  • The Azure Disk CSI Driver Operator provides a storage class named managed-csi that you can use to create persistent volume claims (PVCs). The Azure Disk CSI Driver Operator supports dynamic volume provisioning by allowing storage volumes to be created on-demand, eliminating the need for cluster administrators to pre-provision storage.

  • The Azure Disk CSI driver enables you to create and mount Azure Disk PVs.

About CSI

Storage vendors have traditionally provided storage drivers as part of Kubernetes. With the implementation of the Container Storage Interface (CSI), third-party providers can instead deliver storage plugins using a standard interface without ever having to change the core Kubernetes code.

CSI Operators give OKD users storage options, such as volume snapshots, that are not possible with in-tree volume plugins.

OKD defaults to using an in-tree (non-CSI) plugin to provision Azure Disk storage.

In future OKD versions, volumes provisioned using existing in-tree plugins are planned for migration to their equivalent CSI driver. CSI automatic migration should be seamless. Migration does not change how you use all existing API objects, such as persistent volumes, persistent volume claims, and storage classes. For more information about migration, see CSI automatic migration.

After full migration, in-tree plugins will eventually be removed in later versions of OKD.

Creating a storage class with storage account type

Storage classes are used to differentiate and delineate storage levels and usages. By defining a storage class, you can obtain dynamically provisioned persistent volumes.

When creating a storage class, you can designate the storage account type. This corresponds to your Azure storage account SKU tier. Valid options are Standard_LRS, Premium_LRS, StandardSSD_LRS, UltraSSD_LRS, Premium_ZRS, and StandardSSD_ZRS. For information about finding your Azure SKU tier, see SKU Types.

ZRS has some region limitations. For information about these limitations, see ZRS limitations.

Prerequisites

  • Access to an OKD cluster with administrator rights

Procedure

Use the following steps to create a storage class with a storage account type.

  1. Create a storage class designating the storage account type using a YAML file similar to the following:

    $ oc create -f - << EOF
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: <storage-class> (1)
provisioner: disk.csi.azure.com
parameters:
  skuName: <storage-class-account-type> (2)
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
EOF
    1 Storage class name.
    2 Storage account type. This corresponds to your Azure storage account SKU tier:`Standard_LRS`, Premium_LRS, StandardSSD_LRS, UltraSSD_LRS, Premium_ZRS, StandardSSD_ZRS.

  2. Ensure that the storage class was created by listing the storage classes:

    $ oc get storageclass
    Example output
    $ oc get storageclass
NAME                    PROVISIONER          RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
azurefile-csi           file.csi.azure.com   Delete          Immediate              true                   68m
managed-csi (default)   disk.csi.azure.com   Delete          WaitForFirstConsumer   true                   68m
sc-prem-zrs             disk.csi.azure.com   Delete          WaitForFirstConsumer   true                   4m25s (1)
    1 New storage class with storage account type.

Additional resources