Replication

Container Storage Modules (CSM) for Replication is part of the open-source suite of Kubernetes storage enablers for Dell EMC products.

CSM for Replication project aims to bring Replication & Disaster Recovery capabilities of Dell EMC Storage Arrays to Kubernetes clusters. It helps you replicate groups of volumes using the native replication technology available on the storage array and can provide you a way to restart applications in case of both planned and unplanned migration.

CSM for Replication Capabilities

CSM for Replication provides the following capabilities:

Capability PowerScale Unity PowerStore PowerFlex PowerMax
Replicate data using native storage array based replication no no yes no yes
Create PersistentVolume objects in the cluster representing the replicated volume no no yes no yes
Create DellCSIReplicationGroup objects in the cluster no no yes no yes
Failover & Reprotect applications using the replicated volumes no no yes no yes
Provides a command line utility - repctl for configuring & managing replication related resources across multiple clusters no no yes no yes

Supported Operating Systems/Container Orchestrator Platforms

COP/OS PowerMax PowerStore
Kubernetes 1.20, 1.21, 1.22 1.20, 1.21, 1.22
Red Hat OpenShift X 4.8, 4.9
RHEL 7.x, 8.x 7.x, 8.x
CentOS 7.8, 7.9 7.8, 7.9
Ubuntu 20.04 20.04
SLES 15SP2 15SP2

Supported Storage Platforms

PowerMax PowerStore
Storage Array 5978.479.479, 5978.669.669, 5978.711.711, Unisphere 9.2 1.0.x, 2.0.x

Supported CSI Drivers

CSM for Replication supports the following CSI drivers and versions.

Storage Array CSI Driver Supported Versions
CSI Driver for Dell EMC PowerMax csi-powermax v2.0, v2.1
CSI Driver for Dell EMC PowerStore csi-powerstore v2.0, v2.1

Details

As on the storage arrays, all replication related Kubernetes entities are required/created in pairs -

  1. Pair of Kubernetes Clusters
  2. Pair of replication enabled Storage classes
  3. Pair of PersistentVolumes representing the replicated pair on the storage array
  4. Pair of DellCSIReplicationGroup objects representing the replicated protection groups on the storage array

You can also use a single stretched Kubernetes cluster for protecting your applications. Even in this topology, rest of the objects still exist in pairs.

What it does not do

  • Replicate application manifests within/across clusters
  • Stop applications before the planned/unplanned migration
  • Start applications after the migration
  • Replicate PersistentVolumeClaim objects within/across clusters

CSM for Replication Module Capabilities

CSM for Replication provides the following capabilities:

Capability PowerMax PowerStore PowerScale PowerFlex Unity
Asynchronous replication of PVs accross K8s clusters yes yes no no no
Synchronous replication of PVs accross K8s clusters yes no no no no
Single cluster (stretched) mode replication yes yes no no no
Replication actions (failover, reprotect) yes yes no no no

Supported Platforms

The following matrix provides a list of all supported versions for each Dell EMC Storage product.

Platforms PowerMax PowerStore
Kubernetes 1.20, 1.21, 1.22 1.20, 1.21, 1.22
CSI Driver 2.x 2.x

For compatibility with storage arrays please refer to corresponding CSI drivers

QuickStart

  1. Install all required components:
  • Enable replication during CSI driver installation
  • Install CSM Replication Controller & repctl
  1. Create replication enabled storage classes
  2. Create PersistentVolumeClaim using the replication enabled storage class

How it works

At a high level, the following happens when you create a PersistentVolumeClaim object using a replication enabled storage class -

  1. CSI driver creates protection group on the storage array (if required)
  2. CSI driver creates the volume and adds it to the protection group. There will be a corresponding group and pair on the remote storage array
  3. A DellCSIReplicationGroup object is created in the cluster representing the protection group on the storage array
  4. A replica of the PersistentVolume & DellCSIReplicationGroup is created

You can refer this page for more details about the architecture.

Once the DellCSIReplicationGroup & PersistentVolume objects have been replicated across clusters (or within the same cluster), you can exercise the general Disaster Recovery workflows -

  1. Planned Migration to the target cluster/array
  2. Unplanned Migration to the target cluster/array
  3. Reprotect volumes at the target cluster/array
  4. Maintenance activities like - Suspend, Resume, Establish replication

Deployment

Installation for Dell EMC Container Storage Module (CSM) for Replication

Architecture

High level architecture for CSM for Replication

Cluster Topologies

Supported Cluster Topologies with CSM Replication

Disaster Recovery

Disaster Recovery Workflows

High Availability

High Availability support for CSI PowerMax

Monitoring

DellCSIReplicationGroup Monitoring

Replication Actions

DellCSIReplicationGroup Actions

Tools

repctl tool for Replication feature in detail

Troubleshooting

Troubleshooting guide

Upgrade

Upgrade guide

Uninstall

Dell EMC Container Storage Modules (CSM) for Replication Uninstallation