Storage Classes

This tutorial demonstrates how a cluster administrator can manage storage classes and persistent volumes in KubeSphere.

Introduction

A Persistent Volume (PV) is a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using storage classes. PVs are volume plugins like volumes, but have a lifecycle independent of any individual Pod that uses the PV. PVs can be provisioned either statically or dynamically.

A Persistent Volume Claim (PVC) is a request for storage by a user. It is similar to a Pod. Pods consume node resources and PVCs consume PV resources.

KubeSphere supports dynamic volume provisioning based on storage classes to create PVs.

A storage class provides a way for administrators to describe the classes of storage they offer. Different classes might map to quality-of-service levels, or to backup policies, or to arbitrary policies determined by the cluster administrators. Each storage class has a provisioner that determines what volume plugin is used for provisioning PVs. This field must be specified. For which value to use, please read the official Kubernetes documentation or check with your storage administrator.

The table below summarizes common volume plugins for various provisioners (storage systems).

Prerequisites

You need a user granted a role including the permission of Cluster Management. For example, you can log in to the console as admin directly or create a new role with the permission and assign it to a user.

Create Storage Classes

1. Click Platform in the upper-left corner and select Cluster Management.

2. If you have enabled the multi-cluster feature with member clusters imported, you can select a specific cluster. If you have not enabled the feature, refer to the next step directly.

3. On the Cluster Management page, go to Storage Classes under Storage, where you can create, update, and delete a storage class.

4. To create a storage class, click Create and enter the basic information in the displayed dialog box. When you finish, click Next.

5. In KubeSphere, you can create storage classes for QingCloud-CSI, GlusterFS, and Ceph RBD. Alternatively, you can also create customized storage classes for other storage systems based on your needs. Select a type and click Next.

Common Settings

Some settings are commonly used and shared among storage classes. You can find them as dashboard parameters on the console, which are also indicated by fields or annotations in the StorageClass manifest. You can see the manifest file in YAML format by clicking Edit YAML in the upper-right corner.

Here are parameter descriptions of some commonly used fields in KubeSphere.

For other settings, you need to provide different information for different storage plugins, which, in the manifest, are always indicated under the field parameters. They will be described in detail in the sections below. You can also refer to Parameters in the official documentation of Kubernetes.

QingCloud CSI

QingCloud CSI is a CSI plugin on Kubernetes for the storage service of QingCloud. Storage classes of QingCloud CSI can be created on the KubeSphere console.

Prerequisites

• QingCloud CSI can be used on both public cloud and private cloud of QingCloud. Therefore, make sure KubeSphere has been installed on either of them so that you can use cloud storage services.
• QingCloud CSI Plugin has been installed on your KubeSphere cluster. See QingCloud-CSI Installation for more information.

Settings

For more information about storage class parameters, see QingCloud-CSI user guide.

GlusterFS

GlusterFS is an in-tree storage plugin on Kubernetes, which means you don't need to install a volume plugin additionally.

Prerequisites

The GlusterFS storage system has already been installed. See GlusterFS Installation Documentation for more information.

Settings

For more information about storage class parameters, see GlusterFS in Kubernetes Documentation.

Ceph RBD

Ceph RBD is also an in-tree storage plugin on Kubernetes. The volume plugin is already in Kubernetes, but the storage server must be installed before you create the storage class of Ceph RBD.

As hyperkube images were deprecated since 1.17, in-tree Ceph RBD may not work without hyperkube. Nevertheless, you can use rbd provisioner as a substitute, whose format is the same as in-tree Ceph RBD. The only different parameter is provisioner (i.e Storage System on the KubeSphere console). If you want to use rbd-provisioner, the value of provisioner must be ceph.com/rbd (Enter this value in Storage System in the image below). If you use in-tree Ceph RBD, the value must be kubernetes.io/rbd.

Prerequisites

• The Ceph server has already been installed. See Ceph Installation Documentation for more information.
• Install the plugin if you choose to use rbd-provisioner. Community developers provide charts for rbd provisioner that you can use to install rbd-provisioner by helm.

Settings

For more information about StorageClass parameters, see Ceph RBD in Kubernetes Documentation.

Custom Storage Classes

You can create custom storage classes for your storage systems if they are not directly supported by KubeSphere. The following example shows you how to create a storage class for NFS on the KubeSphere console.

NFS Introduction

NFS (Net File System) is widely used on Kubernetes with the external-provisioner volume plugin nfs-client. You can create the storage class of nfs-client by clicking Custom.

Prerequisites

• An available NFS server.
• The volume plugin nfs-client has already been installed. Community developers provide charts for nfs-client that you can use to install nfs-client by helm.

Common Settings

Parameters

Manage Storage Classes

After you create a storage class, click the name of the storage class to go to its details page. On the details page, click Edit YAML to edit the manifest file of the storage class, or click More to select an operation from the drop-down menu:

• Set as Default Storage Class: Set the storage class as the default storage class in the cluster. Only one default storage class is allowed in a KubeSphere cluster.
• Set Authorization Rule: Set authorization rules so that the storage class can be accessed only in specific projects and workspaces.
• Set Volume Operations: Manage volume features, including: Volume Cloning, Volume Snapshot Creation, and Volume Expansion. Before enabling any features, you should contact your system administrator to confirm that the features are supported by the storage system.
• Set Auto Expansion: Set the system to automatically expand volumes when the remaining volume space is lower than a threshold. You can also enable Restart workload automatically.
• Delete: Delete the storage class.

On the Persistent Volume Claims tab, you can view the PVCs associated to the storage class.

Thanks for the feedback. If you have a specific question about how to use KubeSphere, ask it on Slack. Open an issue in the GitHub repo if you want to report a problem or suggest an improvement.