Is it possible to create pvc on a specific node

[asdfsx]

I have a k8s cluster with 3 node, with lvm-localpv installed.
Now I want to create a lvm pvc on a specific node, but I don't know how
Is it possible to do this?

[abhilashshetty04]

Hi @asdfsx , You can use topology to pass node names. Please make sure VGs are available on all the passed nodes as well.

#452

[todeb]

@asdfsx look at storageclass parameters:
https://openebs.io/docs/user-guides/local-storage-user-guide/local-pv-lvm/configuration/lvm-storageclass-options

either use allowed topologies, or waitforfirstconsumer and then in pod definition define node selector.

[asdfsx]

Thx @todeb
you mean I should create the storage class with WaitForFirstConsumer and allowedTopologies param

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: lvm-sc
allowVolumeExpansion: true
parameters:
  volgroup: "lvmvg"
provisioner: local.csi.openebs.io
volumeBindingMode: WaitForFirstConsumer
allowedTopologies:
- matchLabelExpressions:
  - key: kubernetes.io/hostname
    values:
     - node-1
     - node-2

then create pvc & pod (with nodeName specified )

kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: csi-lvmpv
spec:
  storageClassName: lvm-sc
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 4Gi
---
apiVersion: v1
kind: Pod
metadata:
  name: fio
spec:
  restartPolicy: Never
  nodeName: node-1
  containers:
  - name: perfrunner
    image: openebs/tests-fio
    command: ["/bin/bash"]
    args: ["-c", "while true ;do sleep 50; done"]
    volumeMounts:
       - mountPath: /datadir
         name: fio-vol
    tty: true
  volumes:
  - name: fio-vol
    persistentVolumeClaim:
      claimName: csi-lvmpv

then the pvc will create volume on node-1.

The pvc's creation depends on the first pod consumer, Am I right?

Is there any way to only create a pvc without pod?

[asdfsx]

@abhilashshetty04
I don't really understand what your mean
Can you give an example for passing node names by topology?

[todeb]

if you have waitforfirstconsumer you always need to create a pod. But you can delete it after volume is created.
Also you have an option to create storage class that will provision pvcs only on nodes with specific label.
Then label node you need pvc on then unlabel and label different node if you want to switch.

allowedTopologies:
- matchLabelExpressions:
  - key: mylabel
    values:
    - "true"

Also you can define multiple storageclasses
1st:

allowedTopologies:
- matchLabelExpressions:
  - key: kubernetes.io/hostname
    values:
     - node-1

2nd:

allowedTopologies:
- matchLabelExpressions:
  - key: kubernetes.io/hostname
    values:
     - node-2

On the pvc itself you are not allowed to set the node. You can do this on PV level then do the PVC binding, but that is another story.

This all is k8s defaults not openebs specific so issue should not be followed here. Please read kubernetes and openebs docs.

[asdfsx]

Thx @todeb , I get what your mean!

Right now I'm thinking of add self defined annotation on pvc to specify nodeName, and check the annotation before create lvm volume. Maybe this's a stupid idea.

https://github.com/asdfsx/lvm-localpv/blob/fe94845925024341c49b1b8cfb4e4d101fd2b8c8/pkg/driver/controller.go#L373-L379

I'll try waitforfirstconsumer param first.