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CSM replication aims to bring the replication and disaster recovery capabilities of Dell PowerFlex storage to Kubernetes clusters. It helps you replicate groups of volumes using the native replication capabilities available on PowerFlex and provides a way to restart applications in case of both planned and unplanned migration. Figure 7 shows the logical components that are involved in the functioning of CSM replication module.
CSM for replication consists of four important components:
a) Dell CSI Replication Group (RG), a Kubernetes custom resource.
b) CSM replication sidecar container, which is part of each CSI driver controller pod.
c) CSM replication controller.
d) Repctl client tool to manage related objects.
Dell Replication Group CRD enables volume grouping and supported operations for CSM.
CSM replication sidecar is deployed in each CSI driver controller pod. It has its Controller Manager which manages the PV, PVC, and RG controllers for managing PV creation, binding and other functions within the cluster. The RG controller manages Dell CSI Replication Group instances and its change requests.
CSM Replication Controller is deployed independently of CSI drivers and is responsible for the communication between clusters. It consists of one Controller Manager which manages its own PV, PVC, and RG controllers. The PV controller is responsible for creating PV objects (representing the replicated volumes) in the remote Kubernetes cluster. The RG controller is responsible for creating RG objects in the remote Kubernetes cluster.
For more information about each of these involved components, see CSM architecture.