1.3.19. Storage

Volume Attributes Classes provide a way for administrators to describe "classes" of storage they offer. Different classes might correspond to different quality-of-service levels. Volume Attributes Classes was introduced in OpenShift Container Platform 4.19, and is now generally available in 4.21.

Volume Attributes Classes is available only with AWS Elastic Block Storage (EBS) and Google Cloud Platform (GCP) persistent disk (PD) Container Storage Interface (CSI).

You can apply a Volume Attributes Classes to a persistent volume claim (PVC). If a new Volume Attributes Class becomes available in the cluster, you can update the PVC with the new Volume Attributes Classes if needed.

Volume Attributes Classes have parameters that describe volumes belonging to them. If a parameter is omitted, the default is used at volume provisioning. If a user applies the PVC with a different Volume Attributes Class with omitted parameters, the default value of the parameters might be used depending on the CSI driver implementation. For more information, see the related CSI driver documentation.

For more information, see Volume Attributes Classes.

A snapshot represents the state of the storage volume in a cluster at a particular point in time. Volume snapshots can be used to provision a new volume.

OpenShift Container Platform 4.17 introduced volume snapshot support for the Microsoft Azure File Container Storage Interface (CSI) Driver Operator as a Technology Preview feature. In 4.21, this feature is generally available. Also, Azure File snapshots now supports Network File System (NFS) in addition to Server Message Block (SMB).

For more information, see CSI drivers supported by OpenShift Container Platform and CSI volume snapshots.

Volume cloning duplicates an existing persistent volume (PV) to help protect against data loss in OpenShift Container Platform. You can also use a volume clone just as you would use any standard volume.

OpenShift Container Platform 4.16 introduced volume cloning for the Microsoft Azure File Container Storage Interface (CSI) Driver Operator as a Technology Preview feature. In 4.21, this feature is generally available. Also, Azure File cloning now supports Network File System (NFS) in addition to Server Message Block (SMB).

For more information, see Azure File CSI Driver Operator and CSI volume cloning.

In OpenShift Container Platform 4.21, the CIFS/SMB CSI Driver Operator supports IBM Power (ppc64le).

For more information, see CIFS/SMB CSI Driver Operator.

OpenShift Container Platform 4.19 introduced resizing recovery that stops the expansion controller from indefinitely attempting to expand a volume to an unsupported size request. This feature allows you to recover and provide another smaller resize value for the persistent volume claim (PVC). The new value must be larger than the original volume size.

OpenShift Container Platform 4.21 introduces the pvc.Status.AllocatedResourceStatus field, which shows the status of volume resize attempts. If a user changes the size of their PVCs, this new field allows resource quota to be tracked accurately.

For more information about resizing volumes, see Expanding persistent volumes.

For more information about recovering when resizing volumes, see Recovering from failure when expanding volumes.

This feature allows for dynamically updating the maximum number of storage volumes a node can handle. Without this feature, volume limits are essentially immutable when a node first joins the cluster. If the environment changes—for example, if you attach a new network interface (ENI) that shares a hardware "slot" with your storage—OpenShift Container Platform does not recognize it has fewer slots available for disks, leading to pods becoming stuck.

This feature is only supported on AWS Elastic Block Storage (EBS).

Mutable CSI node allocatable property is supported in OpenShift Container Platform 4.21 as a Technical Preview feature. To enable this feature, you need to enable Feature Gates.

For more information about enabling Technical Preview features, see Feature Gates.

The default installation allows the Google Cloud Platform (GCP) persistent disk (PD) Container Storage Interface (CSI) Driver to impersonate any service account in the Google Cloud project. You can reduce the scope of permissions granted to the GCP PD CSI Driver service account in your Google Cloud project to only the required node service accounts.

For more information about this feature, see Reducing permissions while using the GCP PD CSI Driver Operator.

The API for the Container Storage Interface (CSI) volume group snapshot feature is updated from v1beta1 to v1beta2.

This feature is supported at the Technical Preview level.

For more information, see CSI volume group snapshots.