Unity
Enabling Replication in CSI Unity
Container Storage Modules (CSM) Replication sidecar is a helper container that is installed alongside a CSI driver to facilitate replication functionality. Such CSI drivers must implement dell-csi-extensions
calls.
CSI driver for Dell Unity supports necessary extension calls from dell-csi-extensions
. To be able to provision replicated volumes you would need to do the steps described in these sections.
Before Installation
On Storage Array
Be sure to configure replication between multiple Unity instances using instructions provided by Unity storage.
In Kubernetes
Ensure you installed CRDs and replication controller in your clusters.
To verify you have everything in order you can execute these commands:
- Check controller pods
Pods should be
kubectl get pods -n dell-replication-controller
READY
andRUNNING
- Check that controller config map is properly populated
kubectl get cm -n dell-replication-controller dell-replication-controller-config -o yaml
data
field should be properly populated with cluster-id of your choosing and, if using multi-cluster installation, yourtargets:
parameter should be populated by a list of target clusters IDs.
If you don’t have something installed or something is out-of-place, please refer to installation instructions in installation-repctl or installation.
Installing Driver With Replication Module
To install the driver with replication enabled, you need to ensure you have set
helm parameter controller.replication.enabled
in your copy of example values.yaml
file
(usually called my-unity-settings.yaml
, myvalues.yaml
etc.).
Here is an example of what that would look like:
...
# controller: configure controller specific parameters
controller:
...
# replication: allows to configure replication
replication:
enabled: true
image: dellemc/dell-csi-replicator:v1.2.0
replicationContextPrefix: "unity"
replicationPrefix: "replication.storage.dell.com"
...
You can leave other parameters like image
, replicationContextPrefix
, and replicationPrefix
as they are.
After enabling the replication module, you can continue to install the CSI driver for Unity following the usual installation procedure. Just ensure you’ve added the necessary array connection information to secret.
NOTE: you need to install your driver on ALL clusters where you want to use replication. Both arrays must be accessible from each cluster.
Creating Storage Classes
To provision replicated volumes, you need to create adequately configured storage classes on both the source and target clusters.
A pair of storage classes on the source, and target clusters would be essentially mirrored
copies of one another.
You can create them manually or with the help of repctl
.
Manual Storage Class Creation
You can find a sample replication enabled storage class in the driver repository here.
It will look like this:
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: unity-replication
provisioner: csi-unity.dellemc.com
reclaimPolicy: Delete
volumeBindingMode: Immediate
parameters:
replication.storage.dell.com/isReplicationEnabled: "true"
replication.storage.dell.com/remoteStorageClassName: "unity-replication"
replication.storage.dell.com/remoteClusterID: "target"
replication.storage.dell.com/remoteSystem: "APM000000002"
replication.storage.dell.com/rpo: "5"
replication.storage.dell.com/ignoreNamespaces: "false"
replication.storage.dell.com/volumeGroupPrefix: "csi"
replication.storage.dell.com/remoteStoragePool: pool_002
replication.storage.dell.com/remoteNasServer: nas_124
arrayId: "APM000000001"
protocol: "NFS"
storagePool: pool_001
nasServer: nas_123
Let’s go through each parameter and what it means:
replication.storage.dell.com/isReplicationEnabled
if set totrue
, will mark this storage class as replication enabled, just leave it astrue
.replication.storage.dell.com/remoteStorageClassName
points to the name of the remote storage class. If you are using replication with the multi-cluster configuration you can make it the same as the current storage class name.replication.storage.dell.com/remoteClusterID
represents the ID of a remote cluster. It is the same id you put in the replication controller config map.replication.storage.dell.com/remoteSystem
is the name of the remote system that should match whateverclusterName
you called it inunity-creds
secret.replication.storage.dell.com/rpo
is an acceptable amount of data, which is measured in units of time, that may be lost due to a failure.replication.storage.dell.com/ignoreNamespaces
, if set totrue
Unity driver, it will ignore in what namespace volumes are created and put every volume created using this storage class into a single volume group.replication.storage.dell.com/volumeGroupPrefix
represents what string would be appended to the volume group name to differentiate them.
NOTE: To configure the VolumeGroupPrefix, the name format of '<volumeGroupPrefix>-<namespace>-<Cluster Name>-<rpo>’ cannot be more than 63 characters.
arrayId
is a unique identifier of the storage array you specified in array connection secret.nasServer
id of the Nas server of local array to which the allocated volume will belong.storagePool
is the storage pool of the local array.
After figuring out how storage classes would look, you just need to go and apply them to your Kubernetes clusters with kubectl
.
Storage Class creation with repctl
repctl
can simplify storage class creation by creating a pair of mirrored storage classes in both clusters
(using a single storage class configuration) in one command.
To create storage classes with repctl
you need to fill up the config with necessary information.
You can find an example here, copy it, and modify it to your needs.
If you open this example you can see a lot of similar fields and parameters you can modify in the storage class.
Let’s use the same example from manual installation and see what config would look like:
targetClusterID: "cluster-2"
sourceClusterID: "cluster-1"
name: "unity-replication"
driver: "unity"
reclaimPolicy: "Retain"
replicationPrefix: "replication.storage.dell.com"
remoteRetentionPolicy:
RG: "Retain"
PV: "Retain"
parameters:
arrayId:
source: "APM000000001"
target: "APM000000002"
storagePool:
source: pool_123
target: pool_124
rpo: "0"
ignoreNamespaces: "false"
volumeGroupPrefix: "prefix"
protocol: "NFS"
nasServer:
source: nas_123
target: nas_123
After preparing the config, you can apply it to both clusters with repctl
. Before you do this, ensure you’ve added your clusters to repctl
via the add
command.
To create storage classes just run ./repctl create sc --from-config <config-file>
and storage classes would be applied to both clusters.
After creating storage classes you can make sure they are in place by using ./repctl get storageclasses
command.
Provisioning Replicated Volumes
After installing the driver and creating storage classes, you are good to create volumes using newly created storage classes.
On your source cluster, create a PersistentVolumeClaim using one of the replication-enabled Storage Classes. The CSI Unity driver will create a volume on the array, add it to a VolumeGroup and configure replication using the parameters provided in the replication enabled Storage Class.
Supported Replication Actions
The CSI Unity driver supports the following list of replication actions:
- FAILOVER_REMOTE
- UNPLANNED_FAILOVER_LOCAL
- REPROTECT_LOCAL
- SUSPEND
- RESUME
- SYNC