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StorageClass Parameters Conformance matrix

Following matrix shows standard storageclass parameters for lvm-localpv

Standard StorageClass Parameters

Parameter Values Development Status E2E Coverage
allowVolumeExpansion true Supported Yes
(Test coverage exist for ext4 & xfs)
false Supported
MountOptions Options supported by filesystem Supported Pending
VolumeBindingMode Immediate Supported Yes
WaitForFirstConsumer Supported
Reclaim Policy Retain Supported Yes
(Test coverage exist for Delete reclaim policy)
Delete Supported
allowedTopologies - Supported Yes
Parameters Passing Secrets No Use Case NA
fsType ext2 Supported Yes
(Test coverage exist for ext4 & xfs)
ext3
ext4
xfs
btrfs

LVM Supported StorageClass Parameters

Parameter Values Development Status E2E Coverage
Parameters shared yes Supported Yes
vgpattern Regular expression of volume group name Supported Pending
volgroup Name of volume group Supported Yes
thinProvision yes Supported Pending

StorageClass Options

AllowVolumeExpansion (Optional)

Users can expand the volumes only when allowVolumeExpansion field is set to true in storageclass. If a field is unspecified, then volume expansion is not supported. For more information about expansion workflow click here.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
allowVolumeExpansion: true     ## If set to true then dynamically it allows expansion of volume
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  vgpattern: "lvmvg.*"

MountOptions (Optional)

Volumes that are provisioned via LocalPV-LVM will use the mount options specified in storageclass during volume mounting time inside an application. If a field is unspecified/specified, -o default option will be added to mount the volume. For more information about mount options workflow click here.

Note: Mount options are not validated. If mount options are invalid, then volume mount fails.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  vgpattern: "lvmvg.*"
  mountOptions:    ## Various mount options of volume can be specified here
    - debug

Parameters

LocalPV-LVM storageclass supports various parameters for different use cases. Following are the supported parameters

  • FsType (Optional)

    Admin can specify filesystem in storageclass. LocalPV-LVM CSI-Driver will format block device with specified filesystem and mount in application pod. If fsType is not specified defaults to ext4 filesystem. For more information about filesystem type workflow click here.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
allowVolumeExpansion: true
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  vgpattern: "lvmvg.*"
  fsType: xfs               ## Supported filesystems are ext2, ext3, ext4, xfs & btrfs

  • Shared (Optional)

    lvm-localpv volume mount point can be shared among the multiple pods on the same node. Applications that can share the volume can set value of shared parameter to yes defaults to no. For more information about workflow of share volume click here.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: nvme-lvmsc
allowVolumeExpansion: true
provisioner: local.csi.openebs.io
parameters:
  volgroup: "lvmvg"
  shared: "yes"             ## Parameter that states volume can be shared among multiple pods

  • vgpattern (must parameter if volgroup is not provided, otherwise optional)

    vgpattern specifies the regular expression for the volume groups on node from which the volumes can be created. The vgpattern is the must argument if volgroup parameter is not provided in the storageclass. Here, in this case the driver will pick the volume groups matching the vgpattern with enough free capacity to accomodate the volume and will use the one which has largest capacity available for provisioning the volume. More information about vgpattern workflow is available here.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  vgpattern: "lvmvg.*"     ## vgpattern specifies pattern of lvm volume group name

    if volgroup and vgpattern both the paramaters are defined in the storageclass then volgroup will get higher priority and the driver will use that to provision to the volume.

    Note: Please note that either volgroup or vgpattern should be present in the storageclass parameters to make the provisioning successful.

  • volgroup (must parameter if vgpattern is not provided, otherwise optional)

    volgroup specifies the name of the volume group on nodes from which the volumes will be created. The volgroup is the must argument if vgpattern is not provided in the storageclass.

    Note: Recommended to use vgpattern since volumegroup will be depricated in future.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  volgroup: "lvmvg"       ## volgroup specifies name of lvm volume group

  • thinProvision (Optional)

    For creating thin-provisioned volume, use thinProvision parameter in storage class. It's allowed values are: "yes" and "no". If we don't set thinProvision parameter by default it's value will be no and it will work as thick provisioned volumes. More details about thinProvisioned workflow is available here.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  volgroup: "lvmvg"
  thinProvision: "yes"      ## Parameter that enables thinprovisioning

    Before creating thin provision volume, make ensure that required thin provisioning kernel module dm_thin_pool is loaded on all the nodes.

    To verify if the modules are loaded, run:

    $ lsmod | grep dm_thin_pool

    If modules are not loaded, then execute the following command to load the modules:

    $ modprobe dm_thin_pool

VolumeBindingMode (Optional)

lvm-localpv supports two type volume binding modes that are Immediate & late binding.

  • Immediate: Indicates that volume binding and dynamic provisioning occurs once the PersistentVolumeClaim is created.
  • WaitForFirstConsumer: It is also known as late binding which will delay binding & provisioning of a PersistentVolumeClaim until a pod using the PersistentVolumeClaim is created.
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  vgpattern: "lvmvg.*"
volumeBindingMode: WaitForFirstConsumer     ## It can also replaced by Immediate volume binding mode depends on use case.

Note: More details about VolumeBindingMode is available here.

Reclaim Policy (Optional)

lvm-localpv supports both types of reclaim policy that are Delete & Retain. If not specified defaults to Delete.

  • Delete: Indicates that backend volume resources(PV, LVMVolume) will be delete as soon as after deleting PVC.
  • Retain: Indicates backend volume resources can be recalimed by PVCs or retained the cluster.
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: openebs-lvm
provisioner: local.csi.openebs.io
parameters:
  storage: "lvm"
  vgpattern: "lvmvg.*"
reclaimPolicy: Delete          ## Reclaim policy can be specified here. It also accepts Retain

Note: More details about recalim policy is available here.

StorageClass With Custom Node Labels

There can be a use case where we have certain kinds of Volume Groups present on certain nodes only, and we want a particular type of application to use that VG. We can create a storage class with allowedTopologies and mention all the nodes there where that vg is present:

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

At the same time, you must set env variables in the LocalPV-LVM CSI driver daemon sets (openebs-lvm-localpv-node) so that it can pick the node label as the supported topology. It add "openebs.io/nodename" as default topology key. If the key doesn't exist in the node labels when the CSI LVM driver register, the key will not add to the topologyKeys. Set more than one keys separated by commas.

env:
  - name: OPENEBS_NODE_ID
    valueFrom:
      fieldRef:
        fieldPath: spec.nodeName
  - name: OPENEBS_CSI_ENDPOINT
    value: unix:///plugin/csi.sock
  - name: OPENEBS_NODE_DRIVER
    value: agent
  - name: OPENEBS_NAMESPACE
    value: openebs
  - name: ALLOWED_TOPOLOGIES
    value: "test1,test2"

We can verify that key has been registered successfully with the LVM LocalPV CSI Driver by checking the CSI node object yaml :-

$ kubectl get csinodes pawan-node-1 -oyaml
apiVersion: storage.k8s.io/v1
kind: CSINode
metadata:
  creationTimestamp: "2020-04-13T14:49:59Z"
  name: k8s-node-1
  ownerReferences:
  - apiVersion: v1
    kind: Node
    name: k8s-node-1
    uid: fe268f4b-d9a9-490a-a999-8cde20c4dadb
  resourceVersion: "4586341"
  selfLink: /apis/storage.k8s.io/v1/csinodes/k8s-node-1
  uid: 522c2110-9d75-4bca-9879-098eb8b44e5d
spec:
  drivers:
  - name: local.csi.openebs.io
    nodeID: k8s-node-1
    topologyKeys:
    - openebs.io/nodename
    - test1
    - test2

If you want to change topology keys, just set new env(ALLOWED_TOPOLOGIES) .Check faq for more details.

$ kubectl edit ds -n openebs openebs-lvm-localpv-node

Here we can have volume group of name “lvmvg” created on the nvme disks and want to use this high performing LVM volume group for the applications that need higher IOPS. We can use the above SorageClass to create the PVC and deploy the application using that.

The LocalPV-LVM driver will create the Volume in the volume group “lvmvg” present on the node with fewer of volumes provisioned among the given node list. In the above StorageClass, if there provisioned volumes on node-1 are less, it will create the volume on node-1 only. Alternatively, we can use volumeBindingMode: WaitForFirstConsumer to let the k8s select the node where the volume should be provisioned.

The problem with the above StorageClass is that it works fine if the number of nodes is less, but if the number of nodes is huge, it is cumbersome to list all the nodes like this. In that case, what we can do is, we can label all the similar nodes using the same key value and use that label to create the StorageClass.

user@k8s-master:~ $ kubectl label node k8s-node-2 openebs.io/lvmvg=nvme
node/k8s-node-2 labeled
user@k8s-master:~ $ kubectl label node k8s-node-1 openebs.io/lvmvg=nvme
node/k8s-node-1 labeled

Add "openebs.io/lvmvg" to the LocalPV-LVM CSI driver daemon sets env(ALLOWED_TOPOLOGIES). Now, we can create the StorageClass like this:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: nvme-lvmsc
allowVolumeExpansion: true
parameters:
 volgroup: "lvmvg"
provisioner: local.csi.openebs.io
allowedTopologies:
- matchLabelExpressions:
 - key: openebs.io/lvmvg
   values:
     - nvme

Here, the volumes will be provisioned on the nodes which has label “openebs.io/lvmvg” set as “nvme”.

Note: More details about topology is available here.