High availability volume¶
HwameiStor uses the open source DRBD data synchronization technology to create Highly Available Volume, also known as HA Volume.
Here we use a MySQL application as an example.
Note
The MySQL Yaml file below is from Kubernetes official repo
View StorageClass
¶
StorageClass
"hwameistor-storage-lvm-hdd-ha" uses the parameter replicaNumber: "2"
to enable high availability:
$ kubectl apply -f examples/sc_ha.yaml
$ kubectl get sc hwameistor-storage-lvm-hdd-ha -o yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: hwameistor-storage-lvm-hdd-ha
parameters:
replicaNumber: "2"
convertible: "false"
csi.storage.k8s.io/fstype:xfs
poolClass: HDD
poolType: REGULAR
striped: "true"
volumeKind: LVM
provisioner: lvm.hwameistor.io
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
Create StatefulSet
¶
After HwameiStor and StorageClass
are ready, one command can create MySQL container and its data volume:
Note that volumeClaimTemplates
uses storageClassName: hwameistor-storage-lvm-hdd-ha
:
spec:
volumeClaimTemplates:
- metadata:
name: data
labels:
app: sts-mysql-ha
app.kubernetes.io/name: sts-mysql-ha
spec:
storageClassName: hwameistor-storage-lvm-hdd-ha
accessModes: ["ReadWriteOnce"]
resources:
requests:
storage: 1Gi
View MySQL Pods and PVC/PV
¶
In this example, the MySQL container is scheduled to node k8s-worker-3
.
$ kubectl get po -l app=sts-mysql-ha -o wide
NAME READY STATUS RESTARTS AGE IP NODE
sts-mysql-ha-0 2/2 Running 0 3m08s 10.1.15.151 k8s-worker-1
$ kubectl get pvc -l app=sts-mysql-ha
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGE CLASS AGE VOLUME MODES
data-sts-mysql-ha-0 Bound pvc-5236ee6f-8212-4628-9876-1b620a4c4c36 1Gi RWO hwameistor-storage-lvm-hdd 3m Filesystem
View LocalVolume
and LocalVolumeReplica
objects¶
By viewing LocalVolume(LV)
with the same name as PV
, you can see that the local volume is created on node k8s-worker-1
and node k8s-worker-2
.
$ kubectl get lv pvc-5236ee6f-8212-4628-9876-1b620a4c4c36
NAME POOL REPLICAS CAPACITY ACCESSIBILITY STATE RESOURCE PUBLISHED AGE
pvc-5236ee6f-8212-4628-9876-1b620a4c4c36 LocalStorage_PoolHDD 1 1073741824 Ready-1 k8s-worker-1,k8s-worker-2 3m
LocalVolumeReplica (LVR)
further shows the backend logical volume devices on each node:
kubectl get lvr
NAME CAPACITY NODE STATE SYNCED DEVICE AGE
5236ee6f-8212-4628-9876-1b620a4c4c36-d2kn55 1073741824 k8s-worker-1 Ready true /dev/LocalStorage_PoolHDD-HA/5236ee6f-8212-4628-9876-1b620a4c4c36 4m
5236ee6f-8212-4628-9876-1b620a4c4c36-glm7rf 1073741824 k8s-worker-3 Ready true /dev/LocalStorage_PoolHDD-HA/5236ee6f-8212-4628-9876-1b620a4c4c36 4m