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cStor User Guide

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This user guide section provides the operations need to performed by the User and the Admin for configuring cStor related tasks.

note

With OpenEBS 2.0, the recommended approach to provision cStor Pools is to use cStorPoolCluster(CSPC). For detailed instructions on how to get started with new cStor Operators please refer to the Quickstart guide on Github.

User operations

Provisioning a cStor volume

Monitoring a cStor Volume

Backup and Restore

Snapshot and Clone of a cStor Volume

Upgrading the software version of a cStor volume

Provisioning sample application with cStor

Deleting a cStor Volume

Patching pool deployment by adding or modifying resource limit and requests

Admin operations

Creating cStor storage pools

Setting Pool Policies

Creating cStor storage classes

Setting Storage Polices

Monitoring a cStor Pool

Setting Performance Tunings

Upgrade the software version of a cStor pool

Expanding cStor pool to a new node

Expanding size of a cStor pool instance on a node by expanding the size of cloud disks

Expanding size of a cStor pool instance on a node by add physical/virtual disks to a pool instance

Expanding the cStor Volume Capacity

Scaling up cStor Volume Replica

Scaling down cStor Volume Replica

User Operations

Provisioning a cStor volume

For provisioning a cStor Volume, it requires a cStor Storage Pool and a StorageClass. The configuration and verification of a cStor Storage pool can be checked from here. The configuration and verification of a StorageClass can be checked from here.

Use a similar PVC spec or volumeClaimTemplate to use a StorageClass that is pointing to a pool with real disks. Consider the following parameters while provisioning OpenEBS volumes on real disks.

AccessModes: cStor provides iSCSI targets, which are appropriate for RWO (ReadWriteOnce) access mode and is suitable for all types of databases. For webscale applications like WordPress or any for any other NFS needs, you need RWM (ReadWriteMany) access mode. For RWM, you need NFS provisioner to be deployed along with cStor. See how to provision RWM PVC with OpenEBS .

Size: cStor supports thin provisioning by default, which means you can request any size of the volume through the PVC and get it provisioned. Resize of the volume is not fully supported through the OpenEBS control plane in the current release and it is under active development, see roadmap for more details. Hence it is recommended to give good amount of buffer to the required size of the volume so that you don't need to resize immediately or in a very short time period.

The following shows the example PVC configuration for a Deployment and a StatefulSet application which uses a configured StorageClass to provision a cStor Volume. The provided StorageClass should have been configured with StoragePoolClaim property, so the cStor Volume will be provisioned on the StoragePools associated to the StoragePoolClaim.

Example configuration for requesting OpenEBS volume for a Deployment

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: cstor-pvc-mysql-large
spec:
  storageClassName: openebs-sc-statefulset
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 500Gi

Example configuration for requesting OpenEBS volume for a StatefulSet

spec:
  volumeClaimTemplates:
  - metadata:
      name: elasticdb-vol-openebs
    spec:
      accessModes:
        - ReadWriteOnce
      resources:
        requests:
          storage: 500Gi
      storageClassName: openebs-cstor-pool1-1-replica

Monitoring a cStor Volume

By default the VolumeMonitor is set to ON in the cStor StorageClass. Volume metrics are exported when this parameter is set to ON. Following metrics are supported by cStor as of the current release.

openebs_actual_used # Actual volume size used
openebs_connection_error_total # Total no of connection errors
openebs_connection_retry_total # Total no of connection retry requests
openebs_degraded_replica_count # Total no of degraded/ro replicas
openebs_healthy_replica_count # Total no of healthy replicas
openebs_logical_size # Logical size of volume
openebs_parse_error_total # Total no of parsing errors
openebs_read_block_count # Read Block count of volume
openebs_read_time # Read time on volume
openebs_reads # Read Input/Outputs on Volume
openebs_sector_size # sector size of volume
openebs_size_of_volume # Size of the volume requested
openebs_total_read_bytes # Total read bytes
openebs_total_replica_count # Total no of replicas connected to cas
openebs_total_write_bytes # Total write bytes
openebs_volume_status # Status of volume: (1, 2, 3, 4) = {Offline, Degraded, Healthy, Unknown}
openebs_volume_uptime # Time since volume has registered
openebs_write_block_count # Write Block count of volume
openebs_write_time # Write time on volume
openebs_writes # Write Input/Outputs on Volume

Grafana charts can be built for the above Prometheus metrics.

Snapshot and Clone of a cStor Volume

An OpenEBS snapshot is a set of reference markers for data at a particular point in time. A snapshot act as a detailed table of contents, with accessible copies of data that user can roll back to the required point of instance. Snapshots in OpenEBS are instantaneous and are managed through kubectl.

During the installation of OpenEBS, a snapshot-controller and a snapshot-provisioner are setup which assist in taking the snapshots. During the snapshot creation, snapshot-controller creates VolumeSnapshot and VolumeSnapshotData custom resources. A snapshot-provisioner is used to restore a snapshot as a new Persistent Volume(PV) via dynamic provisioning.

In this section the steps for the creation, clone and deletion a snapshot is provided.

Creating a cStor Snapshot

The following steps will help you to create a snapshot of a cStor volume. For creating the snapshot, you need to create a YAML specification and provide the required PVC name into it. The only prerequisite check is to be performed is to ensure that there is no stale entries of snapshot and snapshot data before creating a new snapshot.

• Copy the following YAML specification into a file called snapshot.yaml.

  apiVersion: volumesnapshot.external-storage.k8s.io/v1
  kind: VolumeSnapshot
  metadata:
    name: snapshot-cstor-volume
    namespace: <Source_PVC_namespace>
  spec:
    persistentVolumeClaimName: cstor-vol1-claim
  

• Edit the snapshot.yaml which is created in previous step to update

  • name :- Name of snapshot which is going to create
  • namespace :- Namespace of source PVC
  • persistentVolumeClaimName :- Source PVC which you are going to take the snapshot.

• Run the following command to create the snapshot of the provided PVC.

  kubectl apply -f snapshot.yaml -n <namespace>
  

  The above command creates a snapshot of the cStor volume and two new CRDs. To list the snapshots, use the following command

  kubectl get volumesnapshot
  kubectl get volumesnapshotdata
  

  Note: All cStor snapshots should be created in the same namespace of source PVC.

Cloning a cStor Snapshot

Once the snapshot is created, restoration from a snapshot or cloning the snapshot is done through a two step process. First create a PVC that refers to the snapshot and then use the PVC to create a new PV. This PVC must refer to a storage class called openebs-snapshot-promoter.

• Copy the following YAML specification into a file called snapshot_claim.yaml.

  apiVersion: v1
  kind: PersistentVolumeClaim
  metadata:
    name: vol-claim-cstor-snapshot
    namespace: <Source_PVC_namespace>
    annotations:
      snapshot.alpha.kubernetes.io/snapshot: snapshot-cstor-volume
  spec:
    storageClassName: openebs-snapshot-promoter
    accessModes: [ "ReadWriteOnce" ]
    resources:
      requests:
        storage: 4G
  

• Edit the YAML file to update

  • name :- Name of the clone PVC
  • namespace :- Same namespace of source PVC
  • The annotation snapshot.alpha.kubernetes.io/snapshot :- Name of the snapshot
  • storage :- The size of the volume being cloned or restored. This should be same as source PVC.

  Note: Size and namespace should be same as the original PVC from which the snapshot was created.

• Run the following command to create a cloned PVC.

  kubectl apply -f snapshot_claim.yaml -n <namespace>
  

• Get the details of newly created PVC for the snapshot.

  kubectl get pvc -n <namespace>
  

• Mount the above PVC in an application YAML to browse the data from the clone.

Note: For deleting the corresponding source volume, it is mandatory to delete the associated clone volumes of this source volume. The source volume deletion will fail if any associated clone volume is present on the cluster.

Deleting a cStor Snapshot

Delete the snapshot using the kubectl command by providing the the same YAML specification that was used to create the snapshot.

kubectl delete -f snapshot.yaml -n <namespace>

This will not affect any PersistentVolumeClaims or PersistentVolumes that were already provisioned using the snapshot. On the other hand, deleting any PersistentVolumeClaims or PersistentVolumes that were provisioned using the snapshot will not delete the snapshot from the OpenEBS backend.

Backup and Restore

OpenEBS volume can be backed up and restored along with the application using OpenEBS velero plugin. It helps the user for backing up the OpenEBS volumes to third party storage location and restore the data whenever it is required. The steps for taking backup and restore are as follows.

Prerequisites

• Latest tested Velero version is 1.4.0.
• Create required storage provider configuration to store the backup.
• Create required OpenEBS storage pools and storage classes on destination cluster.
• Add a common label to all the resources associated to the application that you want to backup. For example, add an application label selector in associated components such as PVC,SVC etc.

Install Velero (Formerly known as ARK)

Follow the instructions at Velero documentation to install and configure Velero.

Steps for Backup

Velero is a utility to back up and restore your Kubernetes resource and persistent volumes.

To do backup/restore of OpenEBS cStor volumes through Velero utility, you need to install and configure OpenEBS velero-plugin. OpenEBS velero-plugin can be installed using the below command:

velero plugin add openebs/velero-plugin:latest

Above command will install the latest OpenEBS velero-plugin image.

If you are using OpenEBS velero-plugin then velero backup command invokes velero-plugin internally and takes a snapshot of cStor volume data and send it to remote storage location as mentioned in 06-volumesnapshotlocation.yaml. The configuration of 06-volumesnapshotlocation.yaml can be done in the next section.

Configure Volumesnapshot Location

To take a backup of cStor volume through Velero, configure VolumeSnapshotLocation with provider openebs.io/cstor-blockstore. Sample YAML file for volumesnapshotlocation can be found at 06-volumesnapshotlocation.yaml from the openebs/velero-plugin repo.

Sample spec for configuring volume snapshot location.

apiVersion: velero.io/v1
kind: VolumeSnapshotLocation
metadata:
  name: <LOCATION_NAME>
  namespace: velero
spec:
  provider: openebs.io/cstor-blockstore
  config:
    bucket: <YOUR_BUCKET>
    prefix: <PREFIX_FOR_BACKUP_NAME>
    backupPathPrefix: <PREFIX_FOR_BACKUP_PATH>
    namespace: <openebs_installed_namespace>
    provider: <GCP_OR_AWS>
    region: <AWS_REGION or minio>

The following are the definition for each parameters.

• name : Provide a snapshot location name. Eg: gcp-default
• bucket : Provide the bucket name created on the cloud provider. Eg: gcpbucket
• prefix : Prefix for backup name. Eg: cstor
• backupPathPrefix: Prefix for backup path. Eg: newbackup. This should be same as prefix mentioned in 05-backupstoragelocation.yaml for keeping all backups at same path. For more details , please refer here.
• namespace : (Optional) Provide the namespace where OpenEBS is installed. OpenEBS velero plugin will automatically take the OpenEBS installed namespace in the absence of this parameter.
• Provider : Provider name. Eg: gcp or aws
• region : Provide region name if cloud provider is AWS or use minio if it is a MinIO bucket.

For configuring parameters for AWS or MinIO in volumesnapshotlocation, refer here for more details.

Example for GCP configuration:

---
apiVersion: velero.io/v1
kind: VolumeSnapshotLocation
metadata:
  name: gcp-default
  namespace: velero
spec:
  provider: openebs.io/cstor-blockstore
  config:
    bucket: gcpbucket
    prefix: cstor
    namespace: openebs
    backupPathPrefix: newbackup
    provider: gcp

After creating the 06-volumesnapshotlocation.yaml with the necessary details, apply the YAML using the following command.

kubectl apply -f 06-volumesnapshotlocation.yaml

Currently supported volumesnapshotlocations for velero-plugin are AWS, GCP and MinIO.

Managing Backups

Take the backup using the below command. Here, you need to get the label of the application.

velero backup create <backup-name> -l app=<app-label-selector> --snapshot-volumes --volume-snapshot-locations=<SNAPSHOT_LOCATION>

Note: SNAPSHOT_LOCATION should be the same as you configured in the 06-volumesnapshotlocation.yaml. You can use --selector as a flag in backup command to filter specific resources or use a combo of --include-namespaces and --exclude-resources to exclude specific resources in the specified namespace. More details can be read from here.

Example:

velero backup create new1 -l app=minio --snapshot-volumes --volume-snapshot-locations=gcp-default

The above command shown in example will take backup of all resources which has a common label app=minio.

After taking backup, verify if backup is taken successfully by using following command.

velero get backup

The following is a sample output.

NAME             STATUS                      CREATED                         EXPIRES   STORAGE LOCATION   SELECTOR
new1             Completed                   2019-06-13 12:44:26 +0530 IST   29d       default            app=minio

From the example mentioned in configure-volumesnapshotlocation, backup files of cStor volumes will be stored at gcpbucket/newbackup/backups/new1/cstor-<pv_name>-new1

You will get more details about the backup using the following command.

velero backup describe <backup_name> 

Example:

velero backup describe new1

Once the backup is completed you should see the Phase marked as Completed and Persistent Volumes field shows the number of successful snapshots.

Steps for Restore

Velero backup can be restored onto a new cluster or to the same cluster. An OpenEBS PVC with the same name as the original PVC will be created and application will run using the restored OpenEBS volume.

Prerequisites

• Create the same namespace and StorageClass configuration of the source PVC in your target cluster.
• If the restoration happens on same cluster where Source PVC was created, then ensure that application and its corresponding components such as Service, PVC,PV and cStorVolumeReplicas are deleted successfully.

On the target cluster, restore the application using the below command.

velero restore create <restore-name> --from-backup <backup-name> --restore-volumes=true

Example:

velero restore create new_restore --from-backup new1 --restore-volumes=true 

The restoration job details can be obtained using the following command.

velero restore get

Once the restore job is completed you should see the corresponding restore job is marked as Completed.

Note: After restoring, you need to set targetip for the volume in all pool pods. This means, if there are 3 cStor pools of same SPC, then you need to set targetip for the volume in all the 3 pool pods. Target IP of the PVC can be find from running the following command.

kubectl get svc -n <openebs_installed namespace>

Output will be similar to the following

NAME                                       TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)                               AGE
admission-server-svc                       ClusterIP   10.4.40.66    <none>        443/TCP                               9h
maya-apiserver-service                     ClusterIP   10.4.34.15    <none>        5656/TCP                              9h
pvc-9b43e8a6-93d2-11e9-a7c6-42010a800fc0   ClusterIP   10.4.43.221   <none>        3260/TCP,7777/TCP,6060/TCP,9500/TCP   8h

In this case, 10.4.43.221 is the service IP of the PV. This target ip is required after login to the pool pod. The steps for updating target ip is as follows:

kubectl exec -it <POOL_POD> -c cstor-pool -n openebs -- bash 

After entering the cstor-pool container, get the dataset name from the output of following command.

zfs list | grep <pv_name>

Update the targetip for the corresponding dataset using the following command.

zfs set io.openebs:targetip=<PVC SERVICE IP> <POOL_NAME/VOLUME_NAME>

After executing the above command, exit from the container session. The above procedure has to be performed on all the other cStor pools of the same SPC.

Verify application status using the following command. Now the application should be running.

kubectl get pod -n <namespace>

Verify PVC status using the following command.

kubectl get pvc -n <namespace>

Scheduling backups

Using velero schedule command, periodic backups are taken.

In case of velero-plugin, this periodic backups are incremental backups which saves storage space and backup time. To restore periodic backup with velero-plugin, refer here for more details. The following command will schedule the backup as per the cron time mentioned .

velero schedule create <backup-schedule-name> --schedule "0 * * * *" --snapshot-volumes volume-snapshot-locations=<SNAPSHOT_LOCATION> -l app=<app-label-selector>

Note: SNAPSHOT_LOCATION should be the same as you configured by using 06-volumesnapshotlocation.yaml

Get the details of backup using the following command

velero backup get

During the first backup iteration of a schedule, full data of the volume will be backed up. After taking the full backup in the first schedule, then it will take the incremental backup as part of the next iteration.

Restore from a Scheduled Backup

Since the backups taken are incremental for a schedule, order of restoring data is important. You need to restore data in the order of the backups created.

For example, below are the available backups for a schedule.

NAME                   STATUS      CREATED                         EXPIRES   STORAGE LOCATION   SELECTOR
sched-20190513104034   Completed   2019-05-13 16:10:34 +0530 IST   29d       gcp                <none>
sched-20190513103534   Completed   2019-05-13 16:05:34 +0530 IST   29d       gcp                <none>
sched-20190513103034   Completed   2019-05-13 16:00:34 +0530 IST   29d       gcp                <none>

Restoration of data need to be done in following way:

velero restore create --from-backup sched-20190513103034 --restore-volumes=true
velero restore create --from-backup sched-20190513103534 --restore-volumes=true
velero restore create --from-backup sched-20190513104034 --restore-volumes=true

Deletion of Backups

To delete a single backup which is not created from scheduled backup, use the following command.

velero backup delete <backup_name>

Note: the deletion of backup will not delete the snapshots created as part of backup from the cStor Storage pool. This can be deleted by following manual steps .

1. First verify the cStor backups created for corresponding cStor volume. To obtain the cStor backups of cStor volume, use the following command by providing the corresponding backup name.

   kubectl get  cstorbackups  -n <backup_namespace> -l openebs.io/backup=<backup_name>  -o=jsonpath='{range .items[*]}{.metadata.labels.openebs\.io/persistent-volume}{"\n"}{end}'
   

2. Delete the corresponding cStor backups using the following command.

   kubectl delete cstorbackups -n <backup_namespace> -l openebs.io/backup=<backup_name>
   

3. To delete the cStor backup completed jobs, use the following command.

   kubectl delete cstorbackupcompleted -n <backup_namespace> -l openebs.io/backup=<backup_name>
   

The deletion of Velero backup schedule doesn't destroy the backup created during the schedule. User need to delete a scheduled backup manually. Use the above steps to delete the scheduled backups.

Upgrading the software version of a cStor volume

The steps are mentioned in Upgrade section. For upgrading cStorVolume, ensure that cStor Pool image is support this cStor volume image. It should also recommended to upgrade the corresponding pool before upgrading cStor volume. The steps for upgrading the cStor volume can be find from here.

Provisioning sample application with cStor

Before provisioning an application ensure that all the below mentioned steps are carried out:

1. Ensure that the filesystem is mounted as per requirement. To know more about mount status click here.
2. Create StoragePool specifying the Blockdevices that are to be used. To know the detailed steps for creation of StoragePool click here. The name specified under metadata in the StoragePoolClaim YAML needs to be mentioned in StorageClass YAML (in the next step). Using this StoragePool create StorageClass by referring here.
3. Once all the above actions have been successfully executed, You can deploy Busybox with cStor volume as follows: Copy the below spec into a file, say demo-busybox-cstor.yaml and update storageClassName to openebs-sc-statefulset.
   

   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: busybox
     labels:
       app: busybox
   spec:
     replicas: 1
     strategy:
       type: RollingUpdate
     selector:
       matchLabels:
         app: busybox
     template:
       metadata:
         labels:
           app: busybox
       spec:
         containers:
         - resources:
              limits:
               cpu: 0.5
           name: busybox
           image: busybox
           command: ['sh', '-c', 'echo Container 1 is Running ; sleep 3600']
           imagePullPolicy: IfNotPresent
           ports:
            - containerPort: 3306
              name: busybox
           volumeMounts:
           - mountPath: /var/lib/mysql
             name: demo-vol1
         volumes:
          - name: demo-vol1
            persistentVolumeClaim:
             claimName: demo-vol1-claim
   ---
   kind: PersistentVolumeClaim
   apiVersion: v1
   metadata:
     name: demo-vol1-claim
   spec:
     storageClassName: openebs-sc-statefulset
     accessModes:
       - ReadWriteOnce
     resources:
       requests:
         storage: 500Gi
   ---
   apiVersion: v1
   kind: Service
   metadata:
     name: busybox-mysql
     labels:
       name: busybox-mysql
   spec:
     ports:
       - port: 3306
         targetPort: 3306
     selector:
         name: busybox
   

   
   Now execute the above yaml file using the below-mentioned command

   kubectl apply -f demo-busybox-cstor.yaml
   

4. To verify whether the application is successfully deployed, execute the following command:
   

   kubectl get pods 
   

   The application pods should be running as displayed below:

   NAME                       READY   STATUS    RESTARTS   AGE
   busybox-66db7d9b88-kkktl   1/1     Running   0          2m16s
   

5. To verify whether the target pod is successfully deployed, execute the following command:
   

   kubectl get pod -n <openebs_installed_namespace> | grep <pvc_name>
   

   The target pod should be running as displayed below:

   NAME                                                              READY   STATUS    RESTARTS   AGE
   pvc-3c8f3d76-0131-11ea-89a5-0cc47ab587b8-target-6566cc7885n4hdt   1/1     Running   0          2m16s
   

The resiliency of the application upon different undesired conditions such as forced reschedule, container crashes or slow network connectivity to cstor target pods can be verified by the following chaos experiments:
OpenEBS target pod failure
OpenEBS target (istgt) container failure
OpenEBS target network delay

Deleting a cStor Volume

The cStor volume can be deleted by deleting the corresponding PVC. This can be done by using the following command.

kubectl delete pvc <PVC_name> -n <PVC_namespace>

The successful deletion of a cStor volume can be verified by running the following commands and ensure there is no entries of particular volume exists as part of the output.

Verify the PVC is deleted successfully using the following command.

kubectl get pvc -n <namespace>

Verify the PV is deleted successfully using the following command:

kubectl get pv

Verify if the cStorVolume is deleted successfully using the following command:

kubectl get cstorvolume -n <openebs_installed_namespace>

Verify if the cStorVolumeReplica(CVR) is deleted successfully using the following command:

kubectl get cvr -n <openebs_installed_namespace>

Verify corresponding cStor Volume target also deleted successfully using the following command:

kubectl get pod -n <openebs_installed_namespace> | grep <pvc_name>

Patching pool deployment by adding or modifying resource limit and requests

1. Create a patch file called "patch.yaml" and add the following content to it. You can change the values based on the Node configuration. Recommended values are 4Gi for limits and 2Gi for requests.

   spec:
     template:
       spec:
         containers:
         - name: cstor-pool
           resources:
             limits:
               memory: 4Gi
             requests:
               memory: 2Gi
   

2. Get the pool deployment using the following command:

   kubectl get deploy -n openebs    
   

3. Patch the corresponding pool deployment using the following command.

   kubectl patch deployment <pool_deployment_name> --patch "$(cat patch.yaml)" -n <openebs_installed_namespace>
   

   Eg:

   kubectl patch deployment <pool_deployment_name> --patch "$(cat patch.yaml)" -n openebs
   

   Note: After patching, the existing pool pod will be terminated and a new pool pod will be created. Repeat the same process for other deployments of the same pool as well one by one once new pool pod is created.

---

Admin Operations

Creating cStor Storage Pools

The cStorStoragePool can be created by specifying the blockDeviceList. The following section will describe the steps in detail.

Create a cStorPool by specifying blockDeviceList

Overview

1. Get the details of blockdevices attached in the cluster.
2. Create a StoragePoolClaim configuration YAML and update the required details.
3. Apply the StoragePoolClaim configuration YAML to create the cStorStoragePool.

Step1:

Get all the blockdevices attached in the cluster with the following command. Modify the following command with appropriate namespace where the OpenEBS is installed. The default namespace where OpenEBS is getting installed is openebs.

kubectl get blockdevice -n <openebs_namespace>

Example:

kubectl get blockdevice -n openebs

The output will be similar to the following.

NAME NODENAME SIZE CLAIMSTATE STATUS AGE blockdevice-1c10eb1bb14c94f02a00373f2fa09b93 gke-ranjith-14-default-pool-da9e1336-mbq9 42949672960 Unclaimed Active 2m39s blockdevice-77f834edba45b03318d9de5b79af0734 gke-ranjith-14-default-pool-da9e1336-d9zq 42949672960 Unclaimed Active 2m47s blockdevice-936911c5c9b0218ed59e64009cc83c8f gke-ranjith-14-default-pool-da9e1336-9j2w 42949672960 Unclaimed Active 2m55s

The details of blockdevice can be get using the following command.

 kubectl describe blockdevice <blockdevicename> -n <openebs_namespace>

Example:

kubectl describe blockdevice blockdevice-1c10eb1bb14c94f02a00373f2fa09b93 -n openebs 

From the output, you will get the hostname and other blockdevice details such as State,Path,Claim State,Capacity etc.

Note: Identify block devices which are unclaimed, unmounted on node and does not contain any filesystem. The above command will help to find these information. More information about the disk mount status on node can be read from here.

Step2:

Create a StoragePoolClaim configuration YAML file called cstor-pool1-config.yaml with the following content. In the following YAML, PoolResourceRequests value is set to 2Gi and PoolResourceLimits value is set to 4Gi. The resources will be shared for all the volume replicas that reside on a pool. The value of these resources can be 2Gi to 4Gi per pool on a given node for better performance. These values can be changed as per the Node configuration for better performance. Refer setting pool policies for more details on the pool policies applicable for cStor.

#Use the following YAMLs to create a cStor Storage Pool.
apiVersion: openebs.io/v1alpha1
kind: StoragePoolClaim
metadata:
  name: cstor-disk-pool
  annotations:
    cas.openebs.io/config: |
      - name: PoolResourceRequests
        value: |-
            memory: 2Gi
      - name: PoolResourceLimits
        value: |-
            memory: 4Gi
spec:
  name: cstor-disk-pool
  type: disk
  poolSpec:
    poolType: striped
  blockDevices:
    blockDeviceList:
    - blockdevice-1c10eb1bb14c94f02a00373f2fa09b93
    - blockdevice-77f834edba45b03318d9de5b79af0734
    - blockdevice-936911c5c9b0218ed59e64009cc83c8f
---

In the above file, change the following parameters as required.

• poolType

  This field represents how the data will be written to the disks on a given pool instance on a node. Supported values are striped, mirrored, raidz and raidz2.

  Note: In OpenEBS, the pool instance does not extend beyond a node. The replication happens at volume level but not at the pool level. See volumes and pools relationship in cStor for a deeper understanding.

• blockDeviceList

  Select the list of selected unclaimed blockDevice CRs which are unmounted and does not contain a filesystem in each participating nodes and enter them under blockDeviceList.

  To get the list of blockDevice CRs, use kubectl get blockdevice -n openebs.

  You must enter all selected blockDevice CRs manually together from the selected nodes.

  When the poolType = mirrored , ensure the number of blockDevice CRs selected from each node are an even number. The data is striped across mirrors. For example, if 4x1TB blockDevice are selected on node1, the raw capacity of the pool instance of cstor-disk-pool on node1 is 2TB.

  When the poolType = striped, the number of blockDevice CRs from each node can be in any number. The data is striped across each blockDevice. For example, if 4x1TB blockDevices are selected on node1, the raw capacity of the pool instance of cstor-disk-pool on that node1 is 4TB.

  When the poolType = raidz, ensure that the number of blockDevice CRs selected from each node are like 3,5,7 etc. The data is written with single parity. For example, if 3x1TB blockDevice are selected on node1, the raw capacity of the pool instance of cstor-disk-pool on node1 is 2TB. 1 disk will be used as a parity disk.

  When the poolType = raidz2, ensure that the number of blockDevice CRs selected from each node are like 6,8,10 etc. The data is written with dual parity. For example, if 6x1TB blockDevice are selected on node1, the raw capacity of the pool instance of cstor-disk-pool on node1 is 4TB. 2 disks will be used for parity.

The number of selected blockDevice CRs across nodes need not be the same. Unclaimed blockDevice CRs which are unmounted on nodes and does not contain any filesystem can be added to the pool spec dynamically as the used capacity gets filled up.

• type

  This value can be either sparse or disk. If you are creating a sparse pool using the sparse disk based blockDevice which are created as part of applying openebs operator YAML, then choose type as sparse. For other blockDevices, choose type as disk.

Step3:

After the StoragePoolClaim configuration YAML spec is created, run the following command to create the pool instances on nodes.

kubectl apply -f cstor-pool1-config.yaml

Verify cStor Pool configuration is created successfully using the following command.

kubectl get spc

The following is an example output.

NAME              AGE
cstor-disk-pool   20s

Verify if cStor Pool is created successfully using the following command.

kubectl get csp

The following is an example output.

NAME                   ALLOCATED   FREE    CAPACITY   STATUS    TYPE      AGE
cstor-disk-pool-2gcb   270K        39.7G   39.8G      Healthy   striped   1m
cstor-disk-pool-9q2f   270K        39.7G   39.8G      Healthy   striped   1m
cstor-disk-pool-ilz1   270K        39.7G   39.8G      Healthy   striped   1m

Verify if cStor pool pods are running using the following command.

kubectl get pod -n <openebs_installed_namespace> | grep -i <spc_name>

Example:

kubectl get pod -n openebs | grep cstor-disk-pool

Example Output:

cstor-disk-pool-2gcb-64876b956b-q8fgp          3/3     Running   0          2m30s
cstor-disk-pool-9q2f-b85ccf6f-6cpdm            3/3     Running   0          2m30s
cstor-disk-pool-ilz1-5587ff79bf-6djjf          3/3     Running   0          2m31s

If all pods are showing are running, then you can use these cStor pools for creating cStor volumes.

Note: The cStor pool can be horizontally scale up on new OpenEBS Node by editing the corresponding pool configuration YAML with the new disks name under blockDeviceList . More details can be found here. If you find any issues, check common issues added in troubleshooting section.

The resiliency of the cStor storage pool can be verified via litmus using cStor-pool-chaos experiment.

Setting Pool Policies

This section captures the policies supported for cStorPools in StoragePoolClaim under cas.openebs.io/config in the name and value pair format.

PoolResourceLimits Policy

This feature allow you to set the limits on memory and cpu for pool pods. The resource and limit value should be in the same format as expected by Kubernetes. The name of SPC can be changed if you need.

apiVersion: openebs.io/v1alpha1
kind: StoragePoolClaim
metadata:
  name: cstor-disk
  annotations:
    cas.openebs.io/config: |
      - name: PoolResourceLimits
        value: |-
            memory: 4Gi
spec:
  name: cstor-disk
  type: disk

PoolResourceRequests Policy

This feature allow you to specify pool resource requests that need to be available before scheduling the containers. If not specified, the default values are used. The following sample configuration will set memory as 2Gi and ephemeral-stroage request value as 100Mi. The memory will be shared for all the volume replicas that reside on a pool. The memory can be 2Gi to 4Gi per pool on a given node for better performance. These values can be changed as per the node configuration for better performance. The below configuration also set the cstor-pool container with 100Mi as ephemeral-storage requests which will avoid erraneous eviction by K8s.

apiVersion: openebs.io/v1alpha1
kind: StoragePoolClaim
metadata:
  name: cstor-disk
  annotations:
    cas.openebs.io/config: |
      - name: PoolResourceRequests
        value: |-
            memory: 2Gi
            ephemeral-storage: "100Mi"
spec:
  name: cstor-disk
  type: disk

Tolerations

cStor pool pods can be ensure that pods are not scheduled onto inappropriate nodes. This can be acheived using taint and tolerations method. If Nodes are tainted to schedule the pods which are tolerating the taint, then cStor pool pods also can be scheduled using this method. Tolerations are applied to cStor pool pods, and allow (but do not require) the pods to schedule onto nodes with matching taints.

apiVersion: openebs.io/v1alpha1
kind: StoragePoolClaim
metadata:
  name: cstor-disk
  annotations:
    cas.openebs.io/config: |
      - name: Tolerations
        value: |-
          t1:
            effect: NoSchedule
            key: nodeA
            operator: Equal
            value: storage
          t2:
            effect: NoSchedule
            key: app
            operator: Equal
            value: storage
spec:
  name: cstor-disk
  type: disk
  maxPools: 3
  poolSpec:
    poolType: striped

AuxResourceLimits Policy

You can specify the AuxResourceLimits which allow you to set limits on side cars.

apiVersion: openebs.io/v1alpha1
kind: StoragePoolClaim
metadata:
  name: cstor-disk
  annotations:
    cas.openebs.io/config: |
      - name:  AuxResourceLimits
        value: |-
            memory: 0.5Gi
            cpu: 100m

AuxResourceRequests Policy

The below configuration will set the cstor-pool side-cars with memory as 0.5Gi, cpu as 100m. This also set the cstor-pool side-cars with ephemeral-storage request 50Mi which will avoid erraneous eviction by K8s.

apiVersion: openebs.io/v1alpha1
kind: StoragePoolClaim
metadata:
  name: cstor-disk
  annotations:
    cas.openebs.io/config: |
      - name: AuxResourceRequests
        value: |-
            memory: 0.5Gi
            cpu: 100m
            ephemeral-storage: "50Mi"

Creating cStor Storage Class

StorageClass definition is an important task in the planning and execution of OpenEBS storage. As detailed in the CAS page, the real power of CAS architecture is to give an independent or a dedicated storage engine like cStor for each workload, so that granular policies can be applied to that storage engine to tune the behaviour or performance as per the workload's need. In OpenEBS policies to the storage engine (in this case it is cStor) through the annotations specified in the StorageClass interface.

Steps to Create a cStor StorageClass

Step1: Decide the cStorPool and get the StoragePoolClaim name associated to it.

Step2: Which application uses it? Decide the replicaCount based on your requirement. OpenEBS doesn't restrict the replica count to set, but only maximum up to 5 replicas are allowed. It depends how users configure it, but for the availability of volumes at least (n/2 + 1) replicas should be up and connected to the target, where n is the replicaCount. The following are some example cases:

• If user configured replica count as 2, then always 2 replicas should be available to perform operations on volume.
• If replica count as 3 it should require at least 2 replicas should be available for volume to be operational.
• If replica count as 5 it should require at least 3 replicas should be available for volume to be operational.

Step3: Are there any other storage policies to be applied to the StorageClass? Refer to the storage policies section for more details on the storage policies applicable for cStor.

Step4: Create a YAML spec file <storage-class-name.yaml> from the master template below, update the pool, replica count and other policies and create the class using kubectl apply -f <storage-class-name.yaml> command.

Step5: Verify the newly created StorageClass using kubectl describe sc <storage-class-name>

Example Configuration of OpenEBS StorageClass

You can create a new StorageClass YAML called openebs-sc-rep3.yaml and add content to it from below. By using this spec, a StorageClass will be created with 3 OpenEBS cStor replicas and will configure them on the pools associated with the StoragePoolClaim:cstor-disk-pool .

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-statefulset
  annotations:
    openebs.io/cas-type: cstor
    cas.openebs.io/config: |
      - name: StoragePoolClaim
        value: "cstor-disk-pool"
      - name: ReplicaCount
        value: "3"
provisioner: openebs.io/provisioner-iscsi

Setting Storage Policies

Below table lists the storage policies supported by cStor. These policies should be built into StorageClass and apply them through PersistentVolumeClaim or VolumeClaimTemplates interface. StoragePoolClaim is the mandatory policy to be specified in all the storage class definitions.

cStor Storage Policy	Mandatory	Default	Purpose
ReplicaCount	No	3	Defines the number of cStor volume replicas
VolumeControllerImage		quay.io/openebs/cstor-volume-mgmt:2.2.0	Dedicated side car for command management like taking snapshots etc. Can be used to apply a specific issue or feature for the workload
VolumeTargetImage		value:quay.io/openebs/cstor-istgt:2.2.0	iSCSI protocol stack dedicated to the workload. Can be used to apply a specific issue or feature for the workload
StoragePoolClaim	Yes	N/A (a valid pool must be provided)	The cStorPool on which the volume replicas should be provisioned
VolumeMonitor		ON	When ON, a volume exporter sidecar is launched to export Prometheus metrics.
VolumeMonitorImage		quay.io/openebs/m-exporter:2.2.0	Used when VolumeMonitor is ON. A dedicated metrics exporter to the workload. Can be used to apply a specific issue or feature for the workload
FSType		ext4	Specifies the filesystem that the volume should be formatted with. Other values are xfs
TargetNodeSelector		Decided by Kubernetes scheduler	Specify the label in key: value format to notify Kubernetes scheduler to schedule cStor target pod on the nodes that match label
TargetResourceLimits		Decided by Kubernetes scheduler	CPU and Memory limits to cStor target pod
TargetResourceRequests		Decided by Kubernetes scheduler	Configuring resource requests that need to be available before scheduling the containers.
TargetTolerations		Decided by Kubernetes scheduler	Configuring the tolerations for target.
AuxResourceLimits		Decided by Kubernetes scheduler	Configuring resource limits on the volume pod side-cars.
AuxResourceRequests		Decided by Kubernetes scheduler	Configure minimum requests like ephemeral storage etc. to avoid erroneous eviction by K8s.
Target Affinity		Decided by Kubernetes scheduler	The policy specifies the label KV pair to be used both on the cStor target and on the application being used so that application pod and cStor target pod are scheduled on the same node.
Target Namespace		openebs	When service account name is specified, the cStor target pod is scheduled in the application's namespace.
cStorStoragePool Replica Anti-Affinity		Decided by Kubernetes scheduler	For StatefulSet applications, to distribute single replica volume on separate nodes .

Storage Pool Claim Policy

You can specify the cStor Pool Claim name using the value for StoragePoolClaim property. This will help you choose cStor storage pool where OpenEBS volume will be created. Following is the default StorageClass template where cStor volume will be created on default cStor Sparse Pool.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-spc
  annotations:
    cas.openebs.io/config: |
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Replica Count Policy

You can specify the cStor volume replica count using the ReplicaCount property. You need to ensure that the replica count should not be more than the pools created in the respective StoragePoolClaim. In the following example, the ReplicaCount is specified as 3. Hence, three cStor volume replicas will be created.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-rep3
  annotations:
    cas.openebs.io/config: |
      - name: ReplicaCount
        value: "3"
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Volume Controller Image Policy

You can specify the cStor Volume Controller Image using the value for VolumeControllerImage property. This will help you choose the volume management image.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-cstor-mgmt-sc
  annotations:
    cas.openebs.io/config: |
      - name: VolumeControllerImage
        value: quay.io/openebs/cstor-volume-mgmt:2.2.0
      - name: StoragePoolClaim
        value: "cstor-disk-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Volume Target Image Policy

You can specify the cStor Target Image using the value for VolumeTargetImage property. This will help you choose the cStor istgt target image.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-cstor-target-sc
  annotations:
    cas.openebs.io/config: |
      - name: VolumeTargetImage
        value:quay.io/openebs/cstor-istgt:2.2.0
      - name: StoragePoolClaim
        value: "cstor-disk-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Volume Monitor Policy

You can specify the cStor volume monitor feature which can be set using value for the VolumeMonitor property. By default, volume monitor is enabled.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-monitoring
  annotations:
    cas.openebs.io/config: |
      - enabled: "true"
        name: VolumeMonitor
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Volume Monitoring Image Policy

You can specify the monitoring image policy for a particular volume using value for VolumeMonitorImage property. The following sample storage class uses the Volume Monitor Image policy.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-monitor-image
  annotations:
    cas.openebs.io/config: |
      - name: VolumeMonitorImage
        value: quay.io/openebs/m-exporter:2.2.0
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Volume File System Type Policy

You can specify the file system type for the cStor volume where application will consume the storage using value for FSType. The following is the sample storage class. Currently OpenEBS support ext4 as the default file system and it also supports XFS.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-fstype
  annotations:
    cas.openebs.io/config: |
      - name: FSType
        value: ext4
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Target NodeSelector Policy

You can specify the TargetNodeSelector where Target pod has to be scheduled using the value for TargetNodeSelector. In following example, node: appnode is the node label.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-targetselector
  annotations:
    cas.openebs.io/config: |
      - name: TargetNodeSelector
        value: |-
            node: appnode
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Target ResourceLimits Policy

You can specify the TargetResourceLimits to restrict the memory and cpu usage of target pod within the given limit using the value for TargetResourceLimits .

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-target-resource
  annotations:
    cas.openebs.io/config: |
      - name: TargetResourceLimits
        value: |-
            memory: 1Gi
            cpu: 100m
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

TargetResourceRequests Policy

You can specify the TargetResourceRequests to specify resource requests that need to be available before scheduling the containers.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: opeenbs-sc-tgt-request
  annotations:
    cas.openebs.io/config: |
      - name: TargetResourceRequests
        value: |-
            ephemeral-storage: "100Mi"
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

TargetTolerations Policy

You can specify the TargetTolerations to specify the tolerations for target.

- name: TargetTolerations
  value: |-
     t1:
       key: "key1"
       operator: "Equal"
       value: "value1"
       effect: "NoSchedule"
     t2:
       key: "key1"
       operator: "Equal"
       value: "value1"
       effect: "NoExecute"

AuxResourceLimits Policy

You can specify the AuxResourceLimits which allow you to set limits on side cars.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-aux-limit
  annotations:
    cas.openebs.io/config: |
      - name:  AuxResourceLimits
        value: |-
            memory: 0.5Gi
            cpu: 100m
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

AuxResourceRequests Policy

This feature is useful in cases where user has to specify minimum requests like ephemeral storage etc. to avoid erroneous eviction by K8s. AuxResourceRequests allow you to set requests on side cars. Requests have to be specified in the format expected by Kubernetes

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-sc-aux-request
  annotations:
    cas.openebs.io/config: |
      - name: AuxResourceRequests
        value: |-
            memory: 0.5Gi
            cpu: 100m
            ephemeral-storage: "100Mi"
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
    openebs.io/cas-type: cstor
provisioner: openebs.io/provisioner-iscsi

Target Affinity Policy

The StatefulSet workloads access the OpenEBS storage volume by connecting to the Volume Target Pod. This policy can be used to co-locate volume target pod on the same node as workload.

The configuration for implementing this policy is different for deployment and StatefulSet applications.

For StatefulSet Applications

In the case of provisioning StatfulSet applications with replication factor greater than "1" and volume replication factor equal to "1", for a given OpenEBS volume, target and replica related to that volume should be scheduled on the same node where the application pod resides. This feature can be achieved by using either of the following approaches.

Approach 1:

In this approach, modification is required on StatefulSet spec and corresponding StorageClass being used in the StatefulSet spec. Add openebs.io/sts-target-affinity: <metadata.name of STS> label in StatefulSet spec to the following fields.

• spec.selector.matchLabels
• spec.template.labels

Example snippet:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: test-application
  labels:
    app: test-application
spec:
  serviceName: test-application
  replicas: 1
  selector:
    matchLabels:
      app: test-application
      openebs.io/sts-target-affinity: test-application
  template:
    metadata:
      labels:
        app: test-application
        openebs.io/sts-target-affinity: test-application

Do the following changes in the StorageClass that is referred in the claimTemplates of this StatefulSet.

• Set volumeBindingMode to WaitForFirstConsumer

Example snippet:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: cstor-sts
  annotations:
    openebs.io/cas-type: cstor
    cas.openebs.io/config: |
      - name: ReplicaCount
        value: "1"
      - name: StoragePoolClaim
        value: "cstor-sparse-pool" 
provisioner: openebs.io/provisioner-iscsi
volumeBindingMode: WaitForFirstConsumer

Approach 2:

This approach is useful when user/tool does not have control over the StatefulSet spec. In this case, it requires a new StorageClass per StatefulSet application.

Add following changes in the StorageClass that is referred to by the claimTemplates of this StatefulSet.

• Add openebs.io/sts-target-affinity: <metadata.name of STS> label to the following fields.
  • metadata.labels
• Set volumeBindingMode to WaitForFirstConsumer

Example snippet:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: cstor-sts
  labels:
    openebs.io/sts-target-affinity: test-application # name of StatefulSet application
  annotations:
    openebs.io/cas-type: cstor
    cas.openebs.io/config: |
      - name: ReplicaCount
        value: "3"
      - name: StoragePoolClaim
        value: "cstor-sparse-pool" 
provisioner: openebs.io/provisioner-iscsi
volumeBindingMode: WaitForFirstConsumer

Note: It is recommended to do application pod stickiness for seamless working of the above approaches. Example YAML spec for STS can be referred from here.

For Deployment Applications

This feature makes use of the Kubernetes Pod Affinity feature that is dependent on the Pod labels. User will need to add the following label to both Application and PVC.

labels:
  openebs.io/target-affinity: <application-unique-label>

You can specify the Target Affinity in both application and OpenEBS PVC using the following way. For Application Pod, it will be similar to the following.

apiVersion: v1
kind: Pod
metadata:
  name: fio-cstor
  labels:
    name: fio-cstor
    openebs.io/target-affinity: fio-cstor

The following is the sample snippet of the PVC to use Target affinity.

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: fio-cstor-claim
  labels:
    openebs.io/target-affinity: fio-cstor

Note: This feature works only for cases where there is a 1-1 mapping between a application and PVC.

Target Namespace

By default, the cStor target pods are scheduled in a dedicated openebs namespace. The target pod also is provided with OpenEBS service account so that it can access the Kubernetes Custom Resource called CStorVolume and Events. This policy, allows the Cluster administrator to specify if the Volume Target pods should be deployed in the namespace of the workloads itself. This can help with setting the limits on the resources on the target pods, based on the namespace in which they are deployed. To use this policy, the Cluster administrator could either use the existing OpenEBS service account or create a new service account with limited access and provide it in the StorageClass as follows:

annotations:
    cas.openebs.io/config: |
      - name: PVCServiceAccountName
        value: "user-service-account"  

The sample service account can be found here.

cStorStoragePool Replica Anti-Affinity

This policy will adds the ability in cStor to correlate and hence distribute single replica volumes across pools which are in turn deployed in separate nodes when application consuming all these volumes is deployed as a StatefulSet.

Below are supported anti-affinity features:

• openebs.io/replica-anti-affinity: <unique_identification_of_app_in_cluster>
• openebs.io/preferred-replica-anti-affinity: <unique_identification_of_app_in_cluster>

Below is an example of a statefulset YAML spec that makes use of openebs.io/replica-anti-affinity:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-cstor-perf
  annotations:
    cas.openebs.io/config: |
      - name: StoragePoolClaim
        value: "cstor-sparse-pool"
      - name: ReplicaCount
        value: "3"
    openebs.io/cas-type: cstor
  name: openebs-cstor-pool-sts
provisioner: openebs.io/provisioner-iscsi
reclaimPolicy: Delete
volumeBindingMode: Immediate
---
apiVersion: v1
kind: Service
metadata:
  labels:
    app: busybox1
  name: busybox1
spec:
  clusterIP: None
  selector:
    app: busybox1
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: busybox1
  labels:
    app: busybox1
spec:
  serviceName: busybox1
  replicas: 1
  selector:
    matchLabels:
      app: busybox1
      openebs.io/replica-anti-affinity: busybox1
  template:
    metadata:
      labels:
        app: busybox1
        openebs.io/replica-anti-affinity: busybox1
    spec:
      terminationGracePeriodSeconds: 1800
      containers:
      - name: busybox1
        image: ubuntu
        imagePullPolicy: IfNotPresent
        command:
          - sleep
          - infinity
        volumeMounts:
        - name: busybox1
          mountPath: /busybox1
  volumeClaimTemplates:
  - metadata:
      name: busybox1
    spec:
      accessModes: [ "ReadWriteOnce" ]
      storageClassName: openebs-cstor-pool-sts
      resources:
        requests:
          storage: 2Gi

Upgrade the Software Version of a cStor pool

The steps for upgrading cStor Pool is mentioned in Upgrade section. Refer Upgrade section for more details.

Monitor a cStor Pool

A new sidecar will run once a cStor pool pod is created.This sidecar will collect the metrics of the corresponding cStorStoragePool. Following metrics are supported by cStor to export the cStorStoragePool usage statistics as Prometheus metrics.

openebs_volume_replica_available_size # Available size of volume replica on a pool
openebs_volume_replica_used_size # Used size of volume replica on a pool
openebs_dispatched_io_count # Dispatched IO's count
openebs_free_pool_capacity # Free capacity in pool
openebs_inflight_io_count # Inflight IO's count
openebs_maya_exporter_version # A metric with a constant '1' value labeled by commit and version from which maya-exporter was built.
openebs_pool_size # Size of pool
openebs_pool_status # Status of pool (0, 1, 2, 3, 4, 5, 6)= {"Offline", "Online", "Degraded", "Faulted", "Removed", "Unavail", "NoPoolsAvailable"}
openebs_read_latency # Read latency on replica
openebs_rebuild_bytes # Rebuild bytes
openebs_rebuild_count # Rebuild count
openebs_rebuild_status # Status of rebuild on replica (0, 1, 2, 3, 4, 5, 6)= {"INIT", "DONE", "SNAP REBUILD INPROGRESS", "ACTIVE DATASET REBUILD INPROGRESS", "ERRORED", "FAILED", "UNKNOWN"}
openebs_replica_status # Status of replica (0, 1, 2, 3) = {"Offline", "Healthy", "Degraded", "Rebuilding"}
openebs_total_rebuild_done # Total number of rebuild done on replica
openebs_sync_count # Total number of sync on replica
openebs_sync_latency # Sync latency on replica
openebs_total_failed_rebuild # Total number of failed rebuilds on replica
openebs_total_read_bytes # Total read in bytes
openebs_total_read_count # Total read io count
openebs_total_rebuild_done # Total number of rebuild done on replica
openebs_total_write_bytes # Total write in bytes
openebs_total_write_count # Total write io count
openebs_used_pool_capacity # Capacity used by pool
openebs_used_pool_capacity_percent # Capacity used by pool in percent
openebs_used_size Used # size of pool and volume
openebs_volume_status # Status of volume (0, 1, 2, 3) = {"Offline", "Healthy", "Degraded", "Rebuilding"}
openebs_write_latency # Write latency on replica
openebs_zfs_command_error # zfs command error counter
openebs_zfs_list_command_error # zfs list command error counter
openebs_zfs_parse_error # zfs parse error counter
openebs_zfs_list_failed_to_initialize_libuzfs_client_error_counter # Total no of failed to initialize libuzfs client error in zfs list command
openebs_zfs_list_no_dataset_available_error_counter #  Total number of no datasets error in zfs list command
openebs_zfs_list_parse_error # Total number of zfs list parse errors 
openebs_zfs_list_request_reject_count # Total number of rejected requests of zfs list
openebs_zfs_stats_command_error # Total number of zfs command errors
openebs_zfs_stats_parse_error_counter # Total number of zfs stats parse errors
openebs_zfs_stats_reject_request_count # Total number of rejected requests of zfs stats
openebs_zpool_list_command_error # Total number of zpool command error counter
openebs_zpool_list_failed_to_initialize_libuzfs_client_error_counter # Total number of initialize libuzfs client error
openebs_zpool_list_incomplete_stdout_error # Total number of incomplete stdout errors
openebs_zpool_list_no_pool_available_error  # Total number of no pool available errors
openebs_zpool_list_parse_error_count # Total number of parsing errors
openebs_zpool_list_reject_request_count # Total number of rejected requests of zpool command

Setting Performance Tunings

Allow users to set available performance tunings in StorageClass based on their workload. Below are the tunings that are required:

• cStor target queue depth
  • This limits the ongoing IO count from client. Default is 32.
• cStor target worker threads
  • Sets the number of threads that are working on above queue. It is mentioned by Luworkers. Default value is 6. In case of better number of cores and RAM, this value can be 16. This means 16 threads will be running for each volume.
• cStor volume replica worker threads
  • This Is associated with cStorVolumeReplica.
  • It is mentioned by ZvolWorkers.
  • Defaults to the number of cores on the machine.
  • In case of better number of cores and RAM, this value can be 16.

Note: These configuration can be only used during volume provisioning. Default values will be used in case of "Invalid/None" values has been provided using configuration.

Example Configuration:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-cstor-pool
  annotations:
    openebs.io/cas-type: cstor
    cas.openebs.io/config: |
      - name: StoragePoolClaim
        value: "sparse-claim-auto"
      - name: QueueDepth
        value: "32"
      - name: Luworkers
        value: "16"
      - name: ZvolWorkers
        value: "16"
provisioner: openebs.io/provisioner-iscsi

Note: For sequential workload, setting luworkers to 1 is good. For random workload, default setting to 6 is good.

Expanding cStor Pool to a New Node

cStorPools can be horizontally scaled when needed typically when a new Kubernetes node is added or when the existing cStorPool instances become full with cStorVolumes. This feature is added in 0.8.1.

The steps for expanding the pool to new nodes is given below.

With specifiying blockDeviceList

If you are following this approach, you should have created cStor Pool initially using the steps provided here. For expanding pool onto a new OpenEBS node, you have to edit corresponding pool configuration(SPC) YAML with the required block device names under the blockDeviceList .

Step 1: Edit the existing pool configuration spec that you originally used and apply it (OR) directly edit the in-use spec file using kubectl edit spc <SPC Name>.

Step 2: Add the new disks names from the new Nodes under the blockDeviceList . You can use kubectl get blockdevice -n <openebs_namespace>to obtains the disk CRs.

Step 3: Apply or save the configuration file and a new cStorPool instance will be created on the expected node.

Step 4: Verify the new pool creation by checking

• If a new cStor Pool POD is created (kubectl get pods -n openebs | grep <pool name>)
• If a new cStorPool CR is created (kubectl get csp -n <openebs_installed_namespace>)

Expanding Size of a cStor Pool Instance on a Node (by adding physical/virtual disks to a pool instance)

A pool instance is local to a node. A pool instance can be started with as small as one disk (in striped mode) or two disks (in mirrored) mode. cStor pool instances support thin provisioning of data, which means that provisioning of any volume size will be successful from a given cstorPool config.

However, as the actual used capacity of the pool is utilized, more disks need to be added. Currently the steps for adding more disks to the existing pool is done through manual operations.You can add more disks to the existing StoragePool with the steps provide here.

Expanding size of a cStor Pool Instance on a Node (by expanding the size of cloud disks)

When you have a cloud disk and which is used for the creation of cStor Storage pool and when you want to expand the existing cStor pool capacity, you can expand the size of the cloud disk and reflect the change in the corresponding cStor storage pool. There by the cStor pool capacity can be increased. The steps for doing this activity is documented here.

Expanding the cStor Volume Capacity

OpenEBS control plane does not support increasing the size of volume seamlessly. Increasing the size of a provisioned volume requires support from Kubernetes kubelet as the existing connection has to be remounted to reflect the new volume size. This can also be tackled with the new CSI plugin where the responsibility of the mount, unmount and remount actions will be held with the vendor CSI plugin rather than the kubelet itself.

OpenEBS team is working on both the CSI plugin as well as the feature to resize the provisioned volume when the PVC is patched for new volume size. Currently this is a manual operation and the steps for expanding the cStor volume is mentioned here.

Scaling up cStor Volume Replica

This section provide the steps for scaling up the replica of a cStor volume.

Prerequisite for scaling up the replicas of cStor volume

• A cStor pool should be available and replica of this cStor volume should not be present on this cStor pool.
• OpenEBS version should be 1.3.0 or more.

Overview

• Get the current replica count of the cStor volume which is mentioned in corresponding StorageClass.
• Find cStor pool(s) where existing cStor volume replica(s) is created.
• Find available cStor pools where new cStor volume replica should be created.
• Verify new cStor Volume Replica(s) is created for the particular volume on the available cStor pool(s).

Steps to perform cStor volume replica scale up:

1. Get the current replica count of the cStor volume which is mentioned in corresponding StorageClass. Get the StorageClass name using the following command:

   kubectl get sc
   

   Example output:

   NAME PROVISIONER AGE openebs-device openebs.io/local 19m openebs-hostpath openebs.io/local 19m openebs-jiva-default openebs.io/provisioner-iscsi 19m openebs-sc-cstor openebs.io/provisioner-iscsi 5m24s openebs-snapshot-promoter volumesnapshot.external-storage.k8s.io/snapshot-promoter 19m standard (default) kubernetes.io/gce-pd

   Perform the following command to get the details of corresponding StorageClass which is used for creating the cStor volume :

   kubectl get sc openebs-sc-cstor -o yaml
   

   In this example, cStor volume is created using this StorageClass openebs-sc-cstor.

   Example snippet of output:

   apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: annotations: cas.openebs.io/config: | - name: StoragePoolClaim value: "cstor-disk-pool" - name: ReplicaCount value: "1" kubectl.kubernetes.io/last-applied-configuration: | {"apiVersion":"storage.k8s.io/v1","kind":"StorageClass","metadata":{"annotations":{"cas.openebs.io/config":"- name: StoragePoolClaim\n value: \"cstor-disk-pool\"\n- name: ReplicaCount\n value: \"1\"\n","openebs.io/cas-type":"cstor"},"name":"openebs-sc-cstor"},"provisioner":"openebs.io/provisioner-iscsi"} openebs.io/cas-type: cstor

   In the above example snippet, it is showing that current cStor volume replica count is 1.

2. Get the PVC details using the following command:

   kubectl get pvc
   

   Example output:

   NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE demo-vol1-claim Bound pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 500Gi RWO openebs-sc-cstor 3h18m

   From the above output, get VOLUME name and use in the following command to get the details of corresponding cStor volume. All commands are peformed by considering above PVC.

   Get the details of cStor volume details using the following command:

   kubectl get cstorvolume -n openebs -l openebs.io/persistent-volume=pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8
   

   Example output:

   NAME STATUS AGE CAPACITY pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 Healthy 20m 500Gi

   Get the details of existing cStor Volume Replica details using the following command:

   kubectl get cvr -n openebs -l openebs.io/persistent-volume=pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8
   

   Example output:

   NAME USED ALLOCATED STATUS AGE pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-hgt4 84.6M 2.88M Healthy 20m

3. Perform the following command to get complete details of the existing cStor volume replica:

   kubectl get cvr pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-hgt4 -n openebs -oyaml
   

   Example snippet of output:

   apiVersion: openebs.io/v1alpha1 kind: CStorVolumeReplica metadata: annotations: cstorpool.openebs.io/hostname: gke-ranjith-scaleup-default-pool-48c9bf17-tb7w isRestoreVol: "false" openebs.io/storage-class-ref: | name: openebs-sc-cstor resourceVersion: 6080 creationTimestamp: "2019-11-09T13:38:44Z" finalizers: - cstorvolumereplica.openebs.io/finalizer generation: 2341 labels: cstorpool.openebs.io/name: cstor-disk-pool-hgt4 cstorpool.openebs.io/uid: ca7b4943-02f4-11ea-b0f6-42010a8000f8 cstorvolume.openebs.io/name: pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 openebs.io/cas-template-name: cstor-volume-create-default-1.4.0 openebs.io/persistent-volume: pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 openebs.io/version: 1.4.0 name: pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-hgt4 namespace: openebs resourceVersion: "388286" selfLink: /apis/openebs.io/v1alpha1/namespaces/openebs/cstorvolumereplicas/pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-hgt4 uid: 3fab1013-02f6-11ea-b0f6-42010a8000f8 spec: capacity: 500G replicaid: C65AE27463F8646017D3F933C204925E targetIP: 10.0.59.89 zvolWorkers: "" status:

   Note down following parameters from the output. This is needed for creating new cStor Volume Replica in step 7.

   • metadata.annotations.openebs.io/storage-class-ref|

     name:

   • metadata.labels.cstorvolume.openebs.io/name

   • metadata.labels.cstorvolume.openebs.io/persistent-volume

   • metadata.labels.cstorvolume.openebs.io/version

   • metadata.namespace

   • spec.capacity

   • spec.targetIP

   • versionDetails.desired

   • versionDetails.status.current

4. Perform the following command to get the cStor Pool where the existing cStor volume replica is created:

   kubectl get cvr pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-hgt4 -n openebs --show-labels |  awk '{print $6}'  | grep -i cstorpool | awk -F'[, ]' '{print $1}'
   

   Example output:

   cstorpool.openebs.io/name=cstor-disk-pool-hgt4

5. Get the available cStor Pools for creating new cStor volume replica. The following command will get the other associated cStor pools details:

   kubectl get csp -l openebs.io/storage-pool-claim=cstor-disk-pool | grep -v cstor-disk-pool-hgt4
   

   Example output:

   NAME ALLOCATED FREE CAPACITY STATUS TYPE AGE cstor-disk-pool-2phf 1.58M 39.7G 39.8G Healthy striped 36m cstor-disk-pool-zm8l 1.60M 39.7G 39.8G Healthy striped 36m

   From the above example output, there are 2 cStor pools available, ie: cstor-disk-pool-2phf and cstor-disk-pool-zm8l. So it is possible to scale up the current volume replica count to 3 from 1.

   Note: If there are no cStor pools available to perform volume replica scale-up , then follow the steps to create new cStor pool by updating existing SPC configuration.

6. Perform the following command to get the details of the cStor Pool where new replica will be created:

   kubectl get csp -n openebs cstor-disk-pool-2phf -oyaml
   

   Example snippet of output:

   apiVersion: openebs.io/v1alpha1 kind: CStorPool metadata: annotations: openebs.io/csp-lease: '{"holder":"openebs/cstor-disk-pool-2phf-5d68b6b7ff-nbslc","leaderTransition":1}' creationTimestamp: "2019-11-09T13:28:17Z" generation: 2196 labels: kubernetes.io/hostname: gke-ranjith-scaleup-default-pool-48c9bf17-tjvs openebs.io/cas-template-name: cstor-pool-create-default-1.4.0 openebs.io/cas-type: cstor openebs.io/storage-pool-claim: cstor-disk-pool openebs.io/version: 1.4.0 name: cstor-disk-pool-2phf ownerReferences: - apiVersion: openebs.io/v1alpha1 blockOwnerDeletion: true controller: true kind: StoragePoolClaim name: cstor-disk-pool uid: ca426d23-02f4-11ea-b0f6-42010a8000f8 resourceVersion: "361683" selfLink: /apis/openebs.io/v1alpha1/cstorpools/cstor-disk-pool-2phf uid: ca657af1-02f4-11ea-b0f6-42010a8000f8

   Note down following parameters from the output. This is needed for creating new cStor Volume Replica in step 7.

   • metadata.annotations.cstorpool.openebs.io/hostname
   • metadata.labels.cstorpool.openebs.io/name
   • metadata.labels.cstorpool.cstorpool.openebs.io/uid

7. Create a CVR in the cStor pool identified in Step 5. Below is the template to create CVR on the identified cStor pool. The values in the template can be filled from CSP YAML related to identified cStor pool, and other CVRs of the volume.

   apiVersion: openebs.io/v1alpha1
   kind: CStorVolumeReplica
   metadata:
    annotations:
      cstorpool.openebs.io/hostname: <Kubernetes_nodename>
      isRestoreVol: "false"
      openebs.io/storage-class-ref: |
        name: <storage_class_name>
    finalizers: 
    - cstorvolumereplica.openebs.io/finalizer
    generation: 1
    labels:
      cstorpool.openebs.io/name: <csp_name>
      cstorpool.openebs.io/uid: <csp_uid>
      cstorvolume.openebs.io/name: <cstor_volume_name>
      openebs.io/cas-template-name: <existing-cStor-volume-cas-template>
      openebs.io/persistent-volume: <persistent_volume_name>
      openebs.io/version: <openebs_version>
    name: <cstor_volume_name>-<csp_name>
    namespace: openebs
   spec:
    capacity: <initial_capacity>
    targetIP: <target_service_ip>
    replicaid: "<md5sum_of_pvc_uid_and_csp_uid>"
   status:
    phase: Recreate
   versionDetails:
     autoUpgrade: false
     desired: <existing_cStor_volume_version>
     status:
       current: <existing_cStor_volume_version>
   

   • <Kubernetes_nodename>: Kubernetes node name where cStor pool exists and new CVR will be created on this Node. This can be obtained from step 6.

   • <storage_class_name>: Storageclass name used to create the cStor volume. It is also available in any existing CVR. This can be obtained from step 3.

   • <csp_name>: Identified cStor pool name where new CVR will be created. This can be obtained from step 6.

   • <csp_uid>: UID of identified cStor pool name where new CVR will be created. This can be obtained from step 6.

   • <persistent_volume_name>: Kubernetes Persistent Volume name of the corresponding cStor volume. This can be obtained from step 3.

   • <openebs_version>: Version of OpenEBS on which this volume exist. This can be obtained from step 3.

   • <cstor_volume_name>: Name of cStor volume. This can be get from step 3.

   • <cstor_volume_name>-<csp_name>: This is the newe CVR name which is going to be created. This should be named as a combination of particular cStor volume name and identified cStor pool name. This can be get from step 3 and step 6.

   • <initial_capacity>: Capacity of the cStor volume. This can be get from step 3.

   • <target_service_ip>: Targetip of corresponding cStor volume. This can be get from step 3.

   • <md5sum_of_pvc_uid_and_csp_uid>: It is the unique value referred to as replicaid in the whole cluster. This can be generated by running the following command:

     echo -n "<pvc-uid>-<csp-uid>" | md5sum | awk '{print toupper($1)}'
     

     Example command:

     echo -n "3f86fcdf-02f6-11ea-b0f6-42010a8000f8-ca657af1-02f4-11ea-b0f6-42010a8000f8" | md5sum | awk '{print toupper($1)}'
     

     In the above example pvc-uid is 3f86fcdf-02f6-11ea-b0f6-42010a8000f8 and csp-uid of identified cStor pool is ca657af1-02f4-11ea-b0f6-42010a8000f8

     Example output:

     113EB77418E30B1A3DA0D9374C4E943C

     Example snippet of filled CVR YAML spec looks like below. :

     apiVersion: openebs.io/v1alpha1
     kind: CStorVolumeReplica
     metadata:
       annotations:
         cstorpool.openebs.io/hostname: gke-ranjith-scaleup-default-pool-48c9bf17-tjvs
         isRestoreVol: "false"
         openebs.io/storage-class-ref: |
           name: openebs-sc-cstor
       finalizers:
       - cstorvolumereplica.openebs.io/finalizer
       generation: 1
       labels:
         cstorpool.openebs.io/name: cstor-disk-pool-2phf
         cstorpool.openebs.io/uid: ca657af1-02f4-11ea-b0f6-42010a8000f8
         cstorvolume.openebs.io/name: pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8
         openebs.io/cas-template-name: cstor-volume-create-default-1.4.0
         openebs.io/persistent-volume: pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8
         openebs.io/version: 1.4.0
       name: pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-2phf
       namespace: openebs
     spec:
       capacity: 500Gi
       targetIP: 10.0.59.89
       replicaid: "113EB77418E30B1A3DA0D9374C4E943C"
     status:
       phase: Recreate
     versionDetails:
       autoUpgrade: false
       desired: 1.4.0
       status:
         current: 1.4.0
     

   In this example, CVR YAML spec is saved as CVR2.yaml .

8. Apply the updated CVR YAML spec to create the new replica of cStor volume using the following command:

   kubectl apply -f cvr2.yaml
   

   Example output:

   cstorvolumereplica.openebs.io/pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-2phf created

9. Verify if new CVR is created successfully using the following command:

   kubectl get cvr -n openebs
   

   Example output:

   NAME USED ALLOCATED STATUS AGE pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-2phf 6K 6K Offline 32s pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-hgt4 158M 3.41M Healthy 4h

   From above output, new replica of the cStor volume is created and STATUS is showing as Offline.

10. Update Desired Replication Factor in cStor volume with new replica count. This can be updated by editing corresponding cStor volume CR YAML.

    kubectl edit cstorvolume pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 -n openebs
    

    The following is the snippet of updated cStor volume CR YAML:

    spec: capacity: 500Gi consistencyFactor: 1 desiredReplicationFactor: 2 iqn: iqn.2016-09.com.openebs.cstor:pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 nodeBase: iqn.2016-09.com.openebs.cstor replicaDetails: knownReplicas: C65AE27463F8646017D3F933C204925E: "11298477277091074483" replicationFactor: 1

    In the above snippet, desiredReplicationFactor is updated to 2 from 1. Example output:

    cstorvolume.openebs.io/pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 edited

11. Verify if the rebuilding has started on new replica of the cStor volume. Once rebuilding has completed, it will update its STATUS as Healthy. Get the latest status of the CVRs using the folloiwng command:

    kubectl get cvr -n openebs
    

    Example output:

    NAME USED ALLOCATED STATUS AGE pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-2phf 158M 3.40M Healthy 8m13s pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8-cstor-disk-pool-hgt4 158M 3.41M Healthy 4h7m

12. Once the new replica of the cStor volume is in Healthy state, check the following parameters of the cStor volume to ensure that details are updated properly.

    • consistencyFactor
    • desiredReplicationFactor
    • spec.replicaDetails.knownReplicas
    • spec.replicationFactor
    • status.replicaDetails.knownReplicas
    • status.replicaStatuses

    The following command will get the details of cStor volume.

    kubectl describe cstorvolume cstorvolume pvc-3f86fcdf-02f6-11ea-b0f6-42010a8000f8 -n openebs
    

    Example snippet:

    API Version: openebs.io/v1alpha1 Kind: CStorVolume ... ...

    Spec: Capacity: 500G Consistency Factor: 2 Desired Replication Factor: 2 Replication Factor: 2 ... ...

    Status: Capacity: 500G Phase: Healthy Replica Details: Known Replicas: C65AE27463F8646017D3F933C204925E: 11298477277091074483 113EB77418E30B1A3DA0D9374C4E943C: 14689006053351698479 ... ...

    In the above snippet, Consistency Factor and Replication Factor is automatically updated and new replica is added under Known Replicas field.

Scaling down cStor Volume Replica

This section provide the steps for scaling down the replica of a cStor volume.

Prerequisites

• All the other cStor volume replicas(CVR) should be in Healthy state except the cStor volume replica that is going to deleted(i.e deleting CVR can be in any state).

• There shouldn't be any ongoing scaleup process. Verify that replicationFactor should be equal to the desiredReplicationFactor from corresponding cStor volume CR specification.

Notes to remember:

• Scaling down one replica at a time is recommended. This means, only one replica at a time should be removed.

Overview

• Get the details of corresponding cStor volume.
• Identify the replica of the cStor volume which needs to be removed.
• Modify the cStor volume specification with required change.
• Verify that the identified volume replica is removed successfully.
• Delete the CVR corresponding to the replicaID entry which was removed from cStor volume.

Steps to perform scaling down of cStor volume replica

1. Perform the following command to get the details of PVC:

   kubectl get pvc
   

   From the output of above command, get VOLUME name and use in the following command to get the details of corresponding cStor volume. All commands are peformed by considering above PVC.

   kubectl get cstorvolume -n openebs -l openebs.io/persistent-volume=pvc-ed6e893a-051d-11ea-a786-42010a8001c9
   

   Example output:

   NAME STATUS AGE CAPACITY pvc-ed6e893a-051d-11ea-a786-42010a8001c9 Healthy 8m9s 500Gi

   Perform the following command to get the details of the replicas of corresponding cStor volume:

   kubectl get cvr -n openebs -l openebs.io/persistent-volume=pvc-ed6e893a-051d-11ea-a786-42010a8001c9
   

   Example output:

   NAME USED ALLOCATED STATUS AGE pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-c0tw 37.5M 2.57M Healthy 8m16s pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-eav6 37.4M 2.57M Healthy 8m16s pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-zcn7 37.4M 2.58M Healthy 8m16s

2. Identify the cStor volume replica from above output which needs to be removed. Then, perform the following command to get the replicaid of the corresponding cStor volume replica. In this example, identified cStor volume replica is pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-c0tw.

   kubectl get cvr pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-c0tw -n openebs -oyaml | grep -i replicaid
   

   Example snippet:

   replicaid: 4858867E8F150C533A2CF30A5D5FD8C6

   From the above output, replicaid of the identified cStor volume replica is 4858867E8F150C533A2CF30A5D5FD8C6.

3. Modify the corresponding cStor volume specification to remove the identified cStor volume replica and update the desiredReplicationFactor. The cStor volume can be edited by using the following command:

   kubectl edit cstorvolume pvc-ed6e893a-051d-11ea-a786-42010a8001c9 -n openebs
   

   The following are the items need to be updated if you are scaling down the replica count from 3 to 2.

   In the below snippet, desiredReplicationFactor is updated to 2 from 3 and removed the replicaid entry of the identified volume replica 4858867E8F150C533A2CF30A5D5FD8C6 from spec.replicaDetails.knownReplicas.

   Example snippet:

   spec: capacity: 500Gi consistencyFactor: 2 desiredReplicationFactor: 2 iqn: iqn.2016-09.com.openebs.cstor:pvc-ed6e893a-051d-11ea-a786-42010a8001c9 nodeBase: iqn.2016-09.com.openebs.cstor replicaDetails: knownReplicas: 2E93FCD50CFA2A0502BE29FF397FA661: "8687568470394952308" 6E1C5FD9EC9C084234C440873D256E93: "7318762175148076215" replicationFactor: 3 status: Init targetIP: 10.0.70.44 targetPort: "3260" targetPortal: 10.0.70.44:3260 status: capacity: 500Gi lastTransitionTime: "2019-11-12T07:32:38Z" lastUpdateTime: "2019-11-12T07:48:08Z" phase: Healthy replicaDetails: knownReplicas: 2E93FCD50CFA2A0502BE29FF397FA661: "8687568470394952308" 6E1C5FD9EC9C084234C440873D256E93: "7318762175148076215" 4858867E8F150C533A2CF30A5D5FD8C6: "3588528959973203834"

4. Verify that the identified replica has been removed from the cStor volume. The following section can be checked to verify the updated details and removal event messages of the cStor volume.

   Removal event message can be checked by describe the corresponding cStor volume using the following command:

   kubectl describe cstorvolume pvc-ed6e893a-051d-11ea-a786-42010a8001c9 -n openebs
   

   Example snippet of output:

   Normal Healthy 18m pvc-ed6e893a-051d-11ea-a786-42010a8001c9-target-58d76bdbd-95hdh, gke-ranjith-scaledown-default-pool-0dece219-jt3d Volume is in Healthy state Warning FailUpdate 92s (x4 over 22m) pvc-ed6e893a-051d-11ea-a786-42010a8001c9-target-58d76bdbd-95hdh, gke-ranjith-scaledown-default-pool-0dece219-jt3d Ignoring changes on volume pvc-ed6e893a-051d-11ea-a786-42010a8001c9 Normal Updated 92s pvc-ed6e893a-051d-11ea-a786-42010a8001c9-target-58d76bdbd-95hdh, gke-ranjith-scaledown-default-pool-0dece219-jt3d Successfully updated the desiredReplicationFactor to 2

   Verify the updated details of cStor volume using the following command:

   kubectl get cstorvolume pvc-ed6e893a-051d-11ea-a786-42010a8001c9 -n openebs -oyaml
   

   Example snippet of output:

   spec: capacity: 500Gi consistencyFactor: 2 desiredReplicationFactor: 2 iqn: iqn.2016-09.com.openebs.cstor:pvc-ed6e893a-051d-11ea-a786-42010a8001c9 nodeBase: iqn.2016-09.com.openebs.cstor replicaDetails: knownReplicas: 2E93FCD50CFA2A0502BE29FF397FA661: "8687568470394952308" 6E1C5FD9EC9C084234C440873D256E93: "7318762175148076215" replicationFactor: 2 status: Init targetIP: 10.0.70.44 targetPort: "3260" targetPortal: 10.0.70.44:3260 status: capacity: 500Gi lastTransitionTime: "2019-11-12T07:32:38Z" lastUpdateTime: "2019-11-12T07:49:38Z" phase: Healthy replicaDetails: knownReplicas: 2E93FCD50CFA2A0502BE29FF397FA661: "8687568470394952308" 6E1C5FD9EC9C084234C440873D256E93: "7318762175148076215" replicaStatuses:

   From the output, the following values are auto updated:

   • replicationFactor : It is updated to 2.

   • status.replicaDetails.knownReplicas : The replicaid entry of identified CVR is removed.

   The status of CVRs corresponding to the cStor volume can be obtained by running the following command:

   kubectl get cvr -n openebs -l openebs.io/persistent-volume=pvc-ed6e893a-051d-11ea-a786-42010a8001c9
   

   Example output:

   NAME USED ALLOCATED STATUS AGE pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-c0tw 58.6M 2.81M Offline 22m pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-eav6 59.5M 2.81M Healthy 22m pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-zcn7 59.5M 2.81M Healthy 22m

   From above output, identified CVR status is changed to Offline.

5. Delete the identified CVR which was removed from cStor volume using the following command:

   kubectl delete cvr pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-c0tw -n openebs
   

   Example output:

   cstorvolumereplica.openebs.io "pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-c0tw" deleted

   Get the latest CVR details of corresponding cStor volume using the following command:

   kubectl get cvr -n openebs -l openebs.io/persistent-volume=pvc-ed6e893a-051d-11ea-a786-42010a8001c9
   

   Example output:

   NAME USED ALLOCATED STATUS AGE pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-eav6 61.8M 2.84M Healthy 23m pvc-ed6e893a-051d-11ea-a786-42010a8001c9-cstor-disk-pool-zcn7 61.9M 2.84M Healthy 23m

See Also:

Understand cStorPools

cStorPool use case for Prometheus

cStor roadmap

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