Overview¶
Introduction¶
CCE allows you to use LVM to combine data volumes on nodes into a storage pool (VolumeGroup) and create LVs for containers to mount. A PV that uses a local persistent volume as the medium is considered local PV.
Compared with the HostPath volume, the local PV can be used in a persistent and portable manner. In addition, the PV of the local PV has the node affinity configuration. The pod mounted to the local PV is automatically scheduled based on the affinity configuration. You do not need to manually schedule the pod to a specific node.
Mounting Modes¶
Local PVs can be mounted only in the following modes:
Using a Local PV Through a Dynamic PV: dynamic creation mode, where you specify a StorageClass during PVC creation and an OBS volume and a PV will be automatically created.
Dynamically Mounting a Local PV to a StatefulSet: Only StatefulSets support this mode. Each pod is associated with a unique PVC and PV. After a pod is rescheduled, the original data can still be mounted to it based on the PVC name. This mode applies to StatefulSets with multiple pods.
Note
Local PVs cannot be used through static PVs. That is, local PVs cannot be manually created and then mounted to workloads through PVCs.
Constraints¶
Local PVs are supported only when the cluster version is v1.21.2-r0 or later and the Everest add-on version is 2.1.23 or later. Version 2.1.23 or later is recommended.
Deleting, removing, resetting, or scaling in a node will cause the PVC/PV data of the local PV associated with the node to be lost, which cannot be restored or used again. For details, see Removing a Node, Deleting a Node, Resetting a Node, and Scaling a Node. In these scenarios, the pod that uses the local PV is evicted from the node. A new pod will be created and stay in the pending state. This is because the PVC used by the pod has a node label, due to which the pod cannot be scheduled. After the node is reset, the pod may be scheduled to the reset node. In this case, the pod remains in the creating state because the underlying logical volume corresponding to the PVC does not exist.
Do not manually delete the corresponding storage pool or detach data disks from the node. Otherwise, exceptions such as data loss may occur.
Local PVs are in non-shared mode and cannot be mounted to multiple workloads or tasks concurrently. Additionally, local PVs cannot be mounted to multiple pods of a workload concurrently.