Resize

We can resize the volume by updating the PVC yaml to the desired size and applying it. The LVM Driver will take care of expanding the volume via lvextend command using "-r" option which will resize the filesystem.

note

Online Volume Expansion for Block mode and btrfs Filesystem mode is supported only from K8s 1.23+ version.

For resize, storageclass that provisions the PVC must support resize. We should have allowVolumeExpansion as true in storageclass.

$ cat sc.yaml

apiVersion: storage.k8s.io/v1

kind: StorageClass

metadata:

name: openebs-lvmpv

allowVolumeExpansion: true

parameters:

fstype: "ext4"

volgroup: "lvmpv-vg"

provisioner: local.csi.openebs.io

$ kubectl apply -f sc.yaml

storageclass.storage.k8s.io/openebs-lvmpv created

Create the PVC using the above storage class.

$ cat pvc.yaml

kind: PersistentVolumeClaim

apiVersion: v1

metadata:

name: csi-lvmpv

spec:

storageClassName: openebs-lvmpv

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 4Gi

$ kubectl apply -f pvc.yaml

persistentvolumeclaim/csi-lvmpv created

OpenEBS LVM driver supports Online Volume expansion, which means that we can expand the volume even if volume is being used by the application and we also do not need to restart the application to use the expanded volume, the LVM Driver will take care of making the space available to it.

note

File system expansion does not happen until an application pod references the resized volume, so if no pods referencing the volume are running, file system expansion will not happen.

Deploy the application using the PVC. Here is a sample yaml for the application:

$ cat fio.yaml

apiVersion: apps/v1

kind: Deployment

metadata:

name: fio

labels:

name: fio

spec:

replicas: 1

selector:

matchLabels:

name: fio

template:

metadata:

labels:

name: fio

spec:

containers:

- resources:

name: perfrunner

image: ljishen/fio

imagePullPolicy: IfNotPresent

command: ["/bin/sh"]

args: ["-c", "while true ;do sleep 50; done"]

volumeMounts:

- mountPath: /datadir

name: fio-vol

volumes:

- name: fio-vol

persistentVolumeClaim:

claimName: csi-lvmpv

$ kubectl apply -f fio.yaml

deployment.apps/fio created

$ kubectl get po

NAME READY STATUS RESTARTS AGE

fio-5b7884bc7b-4mssk 1/1 Running 0 40s

Check the current PVC status.

$ kubectl get pvc

NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE

csi-lvmpv Bound pvc-966b0749-5dea-442f-a584-013cf5d25201 4Gi RWO openebs-lvmpv 85s

Exec into the application pod and check the size.

# df -h /datadir/

Filesystem Size Used Avail Use% Mounted on

/dev/mapper/lvmvg-pvc--966b0749--5dea--442f--a584--013cf5d25201 3.9G 16M 3.9G 1% /datadir

Deploy the application using the PVC which supports volume expansion. Once the application pod is deployed, we will expand the PVC to 5Gi from 4Gi. Edit the PVC yaml and update the size to 5Gi and apply it:

$ cat pvc.yaml

kind: PersistentVolumeClaim

apiVersion: v1

metadata:

name: csi-lvmpv

spec:

storageClassName: openebs-lvmpv

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 5Gi

Apply the above yaml which will resize the volume.

$ kubectl apply -f pvc.yaml

persistentvolumeclaim/csi-lvmpv configured

Check the PVC yaml.

$ kubectl get pvc csi-lvmpv -oyaml

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

annotations:

kubectl.kubernetes.io/last-applied-configuration: |

{"apiVersion":"v1","kind":"PersistentVolumeClaim","metadata":{"annotations":{},"name":"csi-lvmpv","namespace":"default"},"spec":{"accessModes":["ReadWriteOnce"],"r

esources":{"requests":{"storage":"5Gi"}},"storageClassName":"openebs-lvmpv"}}

pv.kubernetes.io/bind-completed: "yes"

pv.kubernetes.io/bound-by-controller: "yes"

volume.beta.kubernetes.io/storage-provisioner: lvm.csi.openebs.io

creationTimestamp: "2020-03-06T06:40:08Z"

finalizers:

- kubernetes.io/pvc-protection

name: csi-lvmpv

namespace: default

resourceVersion: "2547405"

selfLink: /api/v1/namespaces/default/persistentvolumeclaims/csi-lvmpv

uid: 966b0749-5dea-442f-a584-013cf5d25201

spec:

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 5Gi

storageClassName: openebs-lvmpv

volumeMode: Filesystem

volumeName: pvc-966b0749-5dea-442f-a584-013cf5d25201

status:

accessModes:

- ReadWriteOnce

capacity:

storage: 4Gi

conditions:

- lastProbeTime: null

lastTransitionTime: "2020-03-06T06:41:22Z"

message: Waiting for user to (re-)start a pod to finish file system resize of

volume on node.

status: "True"

type: FileSystemResizePending

phase: Bound

See in the message that it is waiting on FileSystemResizePending. The resize request will go to the node where the application pod is running. The LVM driver node agent will resize the filesytem for the application. Keep checking the PVC yaml for FileSystemResizePending to go away, once PVC is resized, the yaml will look like this:

$ kubectl get pvc csi-lvmpv -oyaml

apiVersion: v1

kind: PersistentVolumeClaim

metadata:

annotations:

kubectl.kubernetes.io/last-applied-configuration: |

{"apiVersion":"v1","kind":"PersistentVolumeClaim","metadata":{"annotations":{},"name":"csi-lvmpv","namespace":"default"},"spec":{"accessModes":["ReadWriteOnce"],"resources":{"requests":{"storage":"5Gi"}},"storageClassName":"openebs-lvmpv"}}

pv.kubernetes.io/bind-completed: "yes"

pv.kubernetes.io/bound-by-controller: "yes"

volume.beta.kubernetes.io/storage-provisioner: lvm.csi.openebs.io

creationTimestamp: "2020-03-06T06:40:08Z"

finalizers:

- kubernetes.io/pvc-protection

name: csi-lvmpv

namespace: default

resourceVersion: "2547449"

selfLink: /api/v1/namespaces/default/persistentvolumeclaims/csi-lvmpv

uid: 966b0749-5dea-442f-a584-013cf5d25201

spec:

accessModes:

- ReadWriteOnce

resources:

requests:

storage: 5Gi

storageClassName: openebs-lvmpv

volumeMode: Filesystem

volumeName: pvc-966b0749-5dea-442f-a584-013cf5d25201

status:

accessModes:

- ReadWriteOnce

capacity:

storage: 5Gi

phase: Bound

$ kubectl get pvc

NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE

csi-lvmpv Bound pvc-966b0749-5dea-442f-a584-013cf5d25201 5Gi RWO openebs-lvmpv 28m

Also, we can exec into the application pod and verify the same:

# df -h /datadir/

Filesystem Size Used Avail Use% Mounted on

/dev/mapper/lvmvg-pvc--966b0749--5dea--442f--a584--013cf5d25201 4.9G 16M 4.9G 1% /datadir

As we can see the volume mount point /datadir is showing that it has been resized.