Storage Overview

On-premises clusters offer multiple types of container storage covering various application scenarios through Container Storage Interface (CSI). Additionally, on-premises clusters are fully compatible with Kubernetes native storage services. All these allow you to mount multiple types of storage to containers in on-premises clusters. In addition to Kubernetes volumes such as hostPath, emptyDir, ConfigMaps, and secrets, on-premises clusters support multiple persistent volumes such as file system volumes and local volumes.

• In terms of implementation, storage supports CSI and Kubernetes native storage.

  Category	Description
  CSI	An out-of-tree volume plugin, which specifies the standard container storage API and allows storage vendors to use standard custom storage plugins that are mounted using PVCs and PVs without the need to add their plugin source code to the Kubernetes repository for unified build, compilation, and release.
  Kubernetes native storage	An "in-tree" volume plugin that is built, compiled, and released with the Kubernetes repository.

• In terms of storage media, storage can be classified as cloud storage, local storage, and Kubernetes resource objects.

  Category	Description	Application Scenario
  Cloud storage	The storage media is provided by storage vendors. Storage volumes of this type are mounted using PVCs and PVs.	Data requires high availability or needs to be shared, for example, logs and media resources.
  Local storage	The storage media is the local data disk or memory of the node. The local PV is a custom StorageClass provided by CCE and mounted using PVCs and PVs through the CSI. Other StorageClasses are native to Kubernetes.	Non-HA data requires high I/O and low latency.
  Kubernetes resource objects	ConfigMaps and secrets are resources created in clusters. They are special storage types and are provided by tmpfs (RAM-based file system) on the Kubernetes API server.	ConfigMaps are used to inject configuration data to pods. Secrets are used to transmit sensitive information, such as passwords, to pods.

On-premises clusters are compatible with CSI and support storage products of mainstream storage providers. If you need a storage product, obtain the CSI driver from the storage provider and install the CSI driver.