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Azure File CSI Driver Operator

Overview

OKD is capable of provisioning persistent volumes (PVs) by using the Container Storage Interface (CSI) driver for Microsoft Azure File 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 File storage assets, OKD installs the Azure File CSI Driver Operator and the Azure File CSI driver by default in the openshift-cluster-csi-drivers namespace.

  • The Azure File CSI Driver Operator provides a storage class that is named azurefile-csi that you can use to create persistent volume claims (PVCs).

  • The Azure File CSI driver enables you to create and mount Azure File PVs. The Azure File CSI driver supports dynamic volume provisioning by allowing storage volumes to be created on-demand, eliminating the need for cluster administrators to pre-provision storage.

Azure File CSI Driver Operator does not support:

  • Virtual hard disks (VHD)

  • Network File System (NFS): OKD does not deploy a NFS-backed storage class.

  • Running on nodes with FIPS mode enabled.

For more information about supported features, see Supported CSI drivers and features.

NFS support

OKD supports the Azure File Container Storage Interface (CSI) Driver Operator with Network File System (NFS) with the following restrictions:

  • Creating pods with Azure File NFS volumes that are scheduled to the control plane node causes the mount to be denied.

    To work around this issue: If your control plane nodes are schedulable, and the pods can run on worker nodes, use nodeSelector or Affinity to schedule the pod in worker nodes.

  • FS Group policy behavior:

    Azure File CSI with NFS does not honor the fsGroupChangePolicy requested by pods. Azure File CSI with NFS applies a default OnRootMismatch FS Group policy regardless of the policy requested by the pod.

  • The Azure File CSI Operator does not automatically create a storage class for NFS. You must create it manually. Use a file similar to the following:

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: <storage-class-name> (1)
provisioner: file.csi.azure.com (2)
parameters:
  protocol: nfs (3)
  skuName: Premium_LRS  # available values: Premium_LRS, Premium_ZRS
mountOptions:
  - nconnect=4
    1 Storage class name.
    2 Specifies the Azure File CSI provider.
    3 Specifies NFS as the storage backend protocol.

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.

Additional resources