In myprevious post, shows the basic concepts for Storage in kubernetes, here I want to use some simplified demos to show how these concepts exactly used in a cluster.
Here we use one Emphemral volume -- HostPath type, and a Persistent Volume -- local type as two examples:
HostPath Type
HostPath Type is an empheral volume, even if it will keep the stored file after Pod deleted.
Main Difference:
- No PVC, directly bound with Pod
- Manually create affinity for Pod
apiVersion:v1kind:PersistentVolumemetadata:name:hostpath-pvspec:capacity:storage:100MiaccessModes:-ReadWriteOncehostPath:path:/mnt/data# if not exist will create---apiVersion:v1kind:Podmetadata:name:pod-using-hostpathspec:affinity:nodeAffinity:# host path should have the nodeAffinity itemrequiredDuringSchedulingIgnoredDuringExecution:nodeSelectorTerms:-matchExpressions:-key:kubernetes.io/hostnameoperator:Invalues:-node01volumes:-name:hostpath-volumehostPath:path:/mnt/datacontainers:-name:appimage:busyboxcommand:["sleep","3600"]volumeMounts:-mountPath:/dataname:hostpath-volumeLocal Type
local type is Persistent Volume type, therefore we need create a PVC, and also with a StorageClass.
Main Difference:
- PVC
- SC
- PV need nodeAffinity
- Pod will be assigned according to the node of PV automatically
apiVersion:v1kind:PersistentVolumemetadata:name:local-pvspec:capacity:storage:100MiaccessModes:-ReadWriteOncestorageClassName:local-storage# just a templatelocal:path:/mnt/data# this should existnodeAffinity:required:nodeSelectorTerms:-matchExpressions:-key:kubernetes.io/hostnameoperator:Invalues:-node01---apiVersion:v1kind:PersistentVolumeClaimmetadata:name:local-pvcspec:storageClassName:local-storageaccessModes:-ReadWriteOnceresources:requests:storage:50Mi---apiVersion:v1kind:Podmetadata:name:pod-using-localspec:volumes:-name:local-volumepersistentVolumeClaim:claimName:local-pvccontainers:-name:appimage:busyboxcommand:["sleep","3600"]volumeMounts:-mountPath:/dataname:local-volumeReuse the PV
If we have delete the PV, but still want to continue using the content stored, we need to specify theclaimRef field and make sure thepersistentVolumeReclaimPolicy field isRetain (forlocal type the official documnetDON'T recommend setpersistentVolumeReclaimPolicy: Delete.
for more details of reuse the PV, pls check the official documents:here.
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