In container storage, you can use different types of volumes and mount them to containers in pods as many as you want.
In CCE, container storage is backed both by Kubernetes-native objects, such as emptyDir/hostPath volumes, secrets, and ConfigMaps, and by storage services.
CCE clusters of 1.13 and earlier versions use the storage-driver add-on to connect to storage services to support Kubernetes FlexVolume driver for container storage. The FlexVolume driver has been deprecated in favor of the Container Storage Interface (CSI). The everest add-on for CSI is installed in CCE clusters of 1.15 and later versions by default. For details, see Overview.
- In CCE clusters earlier than Kubernetes 1.13, end-to-end capacity expansion of container storage is not supported, and the PVC capacity is inconsistent with the storage capacity.
- In a cluster of v1.13 or earlier, when an upgrade or bug fix is available for storage functionalities, you only need to install or upgrade the storage-driver add-on. Upgrading the cluster or creating a cluster is not required.
Notes and Constraints
- For clusters created in CCE, Kubernetes v1.15.11 is a transitional version in which the FlexVolume plug-in (storage-driver) is compatible with the CSI plug-in (everest). Clusters of v1.17 and later versions do not support FlexVolume any more. You need to use the everest add-on. For details about CSI and FlexVolume, see Differences Between CSI and FlexVolume Plug-ins.
- The FlexVolume plug-in will be maintained by Kubernetes developers, but new functionality will only be added to CSI. You are advised not to create storage that connects to the FlexVolume plug-in (storage-driver) in CCE any more. Otherwise, the storage resources may not function normally.
Differences Between CSI and FlexVolume Plug-ins
Kubernetes Solution |
CCE Add-on |
Feature |
Usage |
|---|---|---|---|
CSI |
everest |
CSI was developed as a standard for exposing arbitrary block and file storage storage systems to containerized workloads. Using CSI, third-party storage providers can deploy plugins exposing new storage systems in Kubernetes without having to touch the core Kubernetes code. In CCE, the everest add-on is installed by default in clusters of Kubernetes v1.15 and later to connect to storage services (EVS, OBS, SFS, and SFS Turbo). The everest add-on consists of two parts:
For details, see everest. |
The everest add-on is installed by default in clusters of v1.15 and later. CCE will mirror the Kubernetes community by providing continuous support for updated CSI capabilities. |
FlexVolume |
storage-driver |
FlexVolume is an out-of-tree plugin interface that has existed in Kubernetes since version 1.2 (before CSI). CCE provided FlexVolume volumes through the storage-driver add-on installed in clusters of Kubernetes v1.13 and earlier versions. This add-on connects clusters to storage services (EVS, OBS, SFS, and SFS Turbo). For details, see storage-driver. |
For clusters of v1.13 or earlier that have been created, the installed FlexVolume plug-in (the storage-driver add-on in CCE) can still be used. CCE stops providing update support for this add-on, and you are advised to upgrade these clusters. |
- A cluster can use only one type of storage plug-ins.
- The FlexVolume plug-in cannot be replaced by the CSI plug-in in clusters of v1.13 or earlier. You can only upgrade these clusters. For details, see Cluster Upgrade Between Major Versions.
Notice on Using Add-ons
- To use the CSI plug-in (the everest add-on in CCE), your cluster must be using Kubernetes 1.15 or later. This add-on is installed by default when you create a cluster of v1.15 or later. The FlexVolume plug-in (the storage-driver add-on in CCE) is installed by default when you create a cluster of v1.13 or earlier.
- If your cluster is upgraded from v1.13 to v1.15, storage-driver is replaced by everest (v1.1.6 or later) for container storage. The takeover does not affect the original storage functions.
- In version 1.2.0 of the everest add-on, key authentication is optimized when OBS is used. After the everest add-on is upgraded from a version earlier than 1.2.0, you need to restart all workloads that use OBS in the cluster. Otherwise, workloads may not be able to use OBS.
Checking Storage Add-ons
- Log in to the CCE console.
- In the navigation tree on the left, click Add-ons.
- Click the Add-on Instance tab.
- Select a cluster in the upper right corner. The default storage add-on installed during cluster creation is displayed.