OpenEBS for Percona

Introduction

Percona is highly scalable and requires underlying persistent storage to be equally scalable and performing. OpenEBS provides scalable storage for Percona for providing a simple and scalable RDS like solution for both On-Premise and cloud environments.

Advantages of using OpenEBS for Percona database:

• Storage is highly available. Data is replicated on to three different nodes, even across zones. Node upgrades, node failures will not result in unavailability of persistent data.
• For each database instance of Percona, a dedicated OpenEBS workload is allocated so that granular storage policies can be applied. OpenEBS storage controller can be tuned with resources such as memory, CPU and number/type of disks for optimal performance.

Deployment model

As shown above, OpenEBS volumes need to be configured with three replicas for high availability. This configuration works fine when the nodes (hence the cStor pool) is deployed across Kubernetes zones.

Configuration workflow

1. Install OpenEBS

   If OpenEBS is not installed in your K8s cluster, this can done from here. If OpenEBS is already installed, go to the next step.

2. Configure cStor Pool

   If cStor Pool is not configured in your OpenEBS cluster, this can be done from here. If cStor pool is already configured, go to the next step. Sample YAML named openebs-config.yaml for configuring cStor Pool is provided in the Configuration details below.

3. Create Storage Class

   You must configure a StorageClass to provision cStor volume on cStor pool. StorageClass is the interface through which most of the OpenEBS storage policies are defined. In this solution we using a StorageClass to consume the cStor Pool which is created using external disks attached on the Nodes. Since Percona-MySQL is a deployment, it requires high availability of data at Storage level. So cStor volume replicaCount is 3. Sample YAML named openebs-sc-disk.yamlto consume cStor pool with cStor volume replica count as 3 is provided in the configuration details below.

4. Launch and test Percona:

   Create a file called percona-openebs-deployment.yaml and add content from percona-openebs-deployment.yaml given in the configuration details section. Run kubectl apply -f percona-openebs-deployment.yaml to deploy Percona application. For more information, see Percona documentation. In other way, you can use stable Percona image with helm to deploy Percona in your cluster using the following command.

   helm install --name my-release --set persistence.enabled=true,persistence.storageClass=openebs-cstor-disk stable/percona

Reference at openebs.ci

A sample Percona server at https://openebs.ci

Sample YAML for running Percona-mysql using cStor are here

OpenEBS-CI dashboard of Percona

Post deployment Operations

Monitor OpenEBS Volume size

It is not seamless to increase the cStor volume size (refer to the roadmap item). Hence, it is recommended that sufficient size is allocated during the initial configuration.

Monitor cStor Pool size

As in most cases, cStor pool may not be dedicated to just Percona database alone. It is recommended to watch the pool capacity and add more disks to the pool before it hits 80% threshold. See cStorPool metrics.

Maintain volume replica quorum during node upgrades

cStor volume replicas need to be in quorum when applications are deployed as deployment and cStor volume is configured to have 3 replicas. Node reboots may be common during Kubernetes upgrade. Maintain volume replica quorum in such instances. See here for more details.

Configuration details

openebs-config.yaml

#Use the following YAMLs to create a cStor Storage Pool.
# and associated storage class.
apiVersion: openebs.io/v1alpha1
kind: StoragePoolClaim
metadata:
  name: cstor-disk
spec:
  name: cstor-disk
  type: disk
  poolSpec:
    poolType: striped
  # NOTE - Appropriate disks need to be fetched using `kubectl get disks`
  #
  # `Disk` is a custom resource supported by OpenEBS with `node-disk-manager`
  # as the disk operator
# Replace the following with actual disk CRs from your cluster `kubectl get disks`
# Uncomment the below lines after updating the actual disk names.
  disks:
    diskList:
# Replace the following with actual disk CRs from your cluster from `kubectl get disks`
#   - disk-184d99015253054c48c4aa3f17d137b1
#   - disk-2f6bced7ba9b2be230ca5138fd0b07f1
#   - disk-806d3e77dd2e38f188fdaf9c46020bdc
#   - disk-8b6fb58d0c4e0ff3ed74a5183556424d
#   - disk-bad1863742ce905e67978d082a721d61
#   - disk-d172a48ad8b0fb536b9984609b7ee653
---

openebs-sc-disk.yaml

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

percona-openebs-deployment.yaml

---
apiVersion: v1
kind: Pod
metadata:
  name: percona
  labels:
    name: percona
spec:
  securityContext:
    fsGroup: 999
  containers:
  - resources:
      limits:
        cpu: 0.5
    name: percona
    image: percona
    args:
      - "--ignore-db-dir"
      - "lost+found"
    env:
      - name: MYSQL_ROOT_PASSWORD
        value: k8sDem0
    ports:
      - containerPort: 3306
        name: percona
    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-cstor-disk
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 30G

See Also:

OpenEBS architecture

OpenEBS use cases

cStor pools overview