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Persistent storage using Logical Volume Manager Storage

Logical Volume Manager (LVM) Storage uses the TopoLVM CSI driver to dynamically provision local storage on single-node OpenShift clusters.

LVM Storage creates thin-provisioned volumes using Logical Volume Manager and provides dynamic provisioning of block storage on a limited resources single-node OpenShift cluster.

You can create volume groups, persistent volume claims (PVCs), volume snapshots, and volume clones by using LVM Storage.

Logical Volume Manager Storage installation

You can install Logical Volume Manager (LVM) Storage on a single-node OpenShift cluster and configure it to dynamically provision storage for your workloads.

You can deploy LVM Storage on single-node OpenShift clusters by using the OpenShift Container Platform CLI (oc), OpenShift Container Platform web console, or Red Hat Advanced Cluster Management (RHACM).

Prerequisites to install LVM Storage

The prerequisites to install LVM Storage are as follows:

  • Ensure that you have a minimum of 10 milliCPU and 100 MiB of RAM.

  • Ensure that every managed cluster has dedicated disks that are used to provision storage. LVM Storage uses only those disks that are empty and do not contain file system signatures. To ensure that the disks are empty and do not contain file system signatures, wipe the disks before using them.

  • Before installing LVM Storage in a private CI environment where you can reuse the storage devices that you configured in the previous LVM Storage installation, ensure that you have wiped the disks that are not in use. If you do not wipe the disks before installing LVM Storage, you cannot reuse the disks without manual intervention.

    You cannot wipe the disks that are in use.

  • If you want to install LVM Storage by using Red Hat Advanced Cluster Management (RHACM), ensure that you have installed RHACM on an OpenShift Container Platform cluster. See the Installing LVM Storage using RHACM section.

Additional resources

Installing LVM Storage using OpenShift Container Platform Web Console

You can install LVM Storage using the Red Hat OpenShift Container Platform OperatorHub.

Prerequisites

  • You have access to the single-node OpenShift cluster.

  • You are using an account with the cluster-admin and Operator installation permissions.

Procedure

  1. Log in to the OpenShift Container Platform Web Console.

  2. Click Operators → OperatorHub.

  3. Scroll or type LVM Storage into the Filter by keyword box to find LVM Storage.

  4. Click Install.

  5. Set the following options on the Install Operator page:

    1. Update Channel as stable-4.12.

    2. Installation Mode as A specific namespace on the cluster.

    3. Installed Namespace as Operator recommended namespace openshift-storage. If the openshift-storage namespace does not exist, it is created during the operator installation.

    4. Approval Strategy as Automatic or Manual.

      If you select Automatic updates, then the Operator Lifecycle Manager (OLM) automatically upgrades the running instance of your Operator without any intervention.

      If you select Manual updates, then the OLM creates an update request. As a cluster administrator, you must then manually approve that update request to update the Operator to a newer version.

  6. Click Install.

Verification steps

  • Verify that LVM Storage shows a green tick, indicating successful installation.

Uninstalling LVM Storage installed using the OpenShift Web Console

You can uninstall LVM Storage using the Red Hat OpenShift Container Platform Web Console.

Prerequisites

  • You deleted all the applications on the clusters that are using the storage provisioned by LVM Storage.

  • You deleted the persistent volume claims (PVCs) and persistent volumes (PVs) provisioned using LVM Storage.

  • You deleted all volume snapshots provisioned by LVM Storage.

  • You verified that no logical volume resources exist by using the oc get logicalvolume command.

  • You have access to the single-node OpenShift cluster using an account with cluster-admin permissions.

Procedure

  1. From the Operators → Installed Operators page, scroll to LVM Storage or type LVM Storage into the Filter by name to find and click on it.

  2. Click on the LVMCluster tab.

  3. On the right-hand side of the LVMCluster page, select Delete LVMCluster from the Actions drop-down menu.

  4. Click on the Details tab.

  5. On the right-hand side of the Operator Details page, select Uninstall Operator from the Actions drop-down menu.

  6. Select Remove. LVM Storage stops running and is completely removed.

Installing LVM Storage using RHACM

LVM Storage is deployed on single-node OpenShift clusters using Red Hat Advanced Cluster Management (RHACM). You create a Policy object on RHACM that deploys and configures the Operator when it is applied to managed clusters which match the selector specified in the PlacementRule resource. The policy is also applied to clusters that are imported later and satisfy the placement rule.

Prerequisites

  • Access to the RHACM cluster using an account with cluster-admin and Operator installation permissions.

  • Dedicated disks on each single-node OpenShift cluster to be used by LVM Storage.

  • The single-node OpenShift cluster needs to be managed by RHACM, either imported or created.

Procedure

  1. Log in to the RHACM CLI using your OpenShift Container Platform credentials.

  2. Create a namespace in which you will create policies.

    # oc create ns lvms-policy-ns

  3. To create a policy, save the following YAML to a file with a name such as policy-lvms-operator.yaml:

    apiVersion: apps.open-cluster-management.io/v1
kind: PlacementRule
metadata:
  name: placement-install-lvms
spec:
  clusterConditions:
  - status: "True"
    type: ManagedClusterConditionAvailable
  clusterSelector: (1)
    matchExpressions:
    - key: mykey
      operator: In
      values:
      - myvalue
---
apiVersion: policy.open-cluster-management.io/v1
kind: PlacementBinding
metadata:
  name: binding-install-lvms
placementRef:
  apiGroup: apps.open-cluster-management.io
  kind: PlacementRule
  name: placement-install-lvms
subjects:
- apiGroup: policy.open-cluster-management.io
  kind: Policy
  name: install-lvms
---
apiVersion: policy.open-cluster-management.io/v1
kind: Policy
metadata:
  annotations:
    policy.open-cluster-management.io/categories: CM Configuration Management
    policy.open-cluster-management.io/controls: CM-2 Baseline Configuration
    policy.open-cluster-management.io/standards: NIST SP 800-53
  name: install-lvms
spec:
  disabled: false
  remediationAction: enforce
  policy-templates:
  - objectDefinition:
      apiVersion: policy.open-cluster-management.io/v1
      kind: ConfigurationPolicy
      metadata:
        name: install-lvms
      spec:
        object-templates:
        - complianceType: musthave
          objectDefinition:
            apiVersion: v1
            kind: Namespace
            metadata:
              labels:
                openshift.io/cluster-monitoring: "true"
                pod-security.kubernetes.io/enforce: privileged
                pod-security.kubernetes.io/audit: privileged
                pod-security.kubernetes.io/warn: privileged
              name: openshift-storage
        - complianceType: musthave
          objectDefinition:
            apiVersion: operators.coreos.com/v1
            kind: OperatorGroup
            metadata:
              name: openshift-storage-operatorgroup
              namespace: openshift-storage
            spec:
              targetNamespaces:
              - openshift-storage
        - complianceType: musthave
          objectDefinition:
            apiVersion: operators.coreos.com/v1alpha1
            kind: Subscription
            metadata:
              name: lvms
              namespace: openshift-storage
            spec:
              installPlanApproval: Automatic
              name: lvms-operator
              source: redhat-operators
              sourceNamespace: openshift-marketplace
        remediationAction: enforce
        severity: low
  - objectDefinition:
      apiVersion: policy.open-cluster-management.io/v1
      kind: ConfigurationPolicy
      metadata:
        name: lvms
      spec:
        object-templates:
           - complianceType: musthave
             objectDefinition:
               apiVersion: lvm.topolvm.io/v1alpha1
               kind: LVMCluster
               metadata:
                 name: my-lvmcluster
                 namespace: openshift-storage
               spec:
                 storage:
                   deviceClasses:
                   - name: vg1
                     deviceSelector: (2)
                       paths:
                       - /dev/disk/by-path/pci-0000:87:00.0-nvme-1
                       - /dev/disk/by-path/pci-0000:88:00.0-nvme-1
                     thinPoolConfig:
                       name: thin-pool-1
                       sizePercent: 90
                       overprovisionRatio: 10
                     nodeSelector: (3)
                       nodeSelectorTerms:
                       - matchExpressions:
                           - key: app
                             operator: In
                             values:
                             - test1
        remediationAction: enforce
        severity: low
    1 Replace the key and value in PlacementRule.spec.clusterSelector to match the labels set on the single-node OpenShift clusters on which you want to install LVM Storage.
    2 To control or restrict the volume group to your preferred disks, you can manually specify the local paths of the disks in the deviceSelector section of the LVMCluster YAML.
    3 To add a node filter, which is a subset of the additional worker nodes, specify the required filter in the nodeSelector section. LVM Storage detects and uses the additional worker nodes when the new nodes show up.

    This nodeSelector node filter matching is not the same as the pod label matching.

  4. Create the policy in the namespace by running the following command:

    # oc create -f policy-lvms-operator.yaml -n lvms-policy-ns (1)
    1 The policy-lvms-operator.yaml is the name of the file to which the policy is saved.

    This creates a Policy, a PlacementRule, and a PlacementBinding object in the lvms-policy-ns namespace. The policy creates a Namespace, OperatorGroup, Subscription, and LVMCluster resource on the clusters that match the placement rule. This deploys the Operator on the single-node OpenShift clusters which match the selection criteria and configures it to set up the required resources to provision storage. The Operator uses all the disks specified in the LVMCluster CR. If no disks are specified, the Operator uses all the unused disks on the single-node OpenShift node.

    After a device is added to the LVMCluster, it cannot be removed.
Additional resources

Uninstalling LVM Storage installed using RHACM

To uninstall LVM Storage that you installed using RHACM, you need to delete the RHACM policy that you created for deploying and configuring the Operator.

When you delete the RHACM policy, the resources that the policy has created are not removed. You need to create additional policies to remove the resources.

As the created resources are not removed when you delete the policy, you need to perform the following steps:

  1. Remove all the Persistent volume claims (PVCs) and volume snapshots provisioned by LVM Storage.

  2. Remove the LVMCluster resources to clean up Logical Volume Manager resources created on the disks.

  3. Create an additional policy to uninstall the Operator.

Prerequisites

  • Ensure that the following are deleted before deleting the policy:

    • All the applications on the managed clusters that are using the storage provisioned by LVM Storage.

    • PVCs and persistent volumes (PVs) provisioned using LVM Storage.

    • All volume snapshots provisioned by LVM Storage.

  • Ensure you have access to the RHACM cluster using an account with a cluster-admin role.

Procedure

  1. In the OpenShift CLI (oc), delete the RHACM policy that you created for deploying and configuring LVM Storage on the hub cluster by using the following command:

    # oc delete -f policy-lvms-operator.yaml -n lvms-policy-ns (1)
    1 The policy-lvms-operator.yaml is the name of the file to which the policy was saved.

  2. To create a policy for removing the LVMCluster resource, save the following YAML to a file with a name such as lvms-remove-policy.yaml. This enables the Operator to clean up all Logical Volume Manager resources that it created on the cluster.

    apiVersion: policy.open-cluster-management.io/v1
kind: Policy
metadata:
  name: policy-lvmcluster-delete
  annotations:
    policy.open-cluster-management.io/standards: NIST SP 800-53
    policy.open-cluster-management.io/categories: CM Configuration Management
    policy.open-cluster-management.io/controls: CM-2 Baseline Configuration
spec:
  remediationAction: enforce
  disabled: false
  policy-templates:
    - objectDefinition:
        apiVersion: policy.open-cluster-management.io/v1
        kind: ConfigurationPolicy
        metadata:
          name: policy-lvmcluster-removal
        spec:
          remediationAction: enforce (1)
          severity: low
          object-templates:
            - complianceType: mustnothave
              objectDefinition:
                kind: LVMCluster
                apiVersion: lvm.topolvm.io/v1alpha1
                metadata:
                  name: my-lvmcluster
                  namespace: openshift-storage (2)
---
apiVersion: policy.open-cluster-management.io/v1
kind: PlacementBinding
metadata:
  name: binding-policy-lvmcluster-delete
placementRef:
  apiGroup: apps.open-cluster-management.io
  kind: PlacementRule
  name: placement-policy-lvmcluster-delete
subjects:
  - apiGroup: policy.open-cluster-management.io
    kind: Policy
    name: policy-lvmcluster-delete
---
apiVersion: apps.open-cluster-management.io/v1
kind: PlacementRule
metadata:
  name: placement-policy-lvmcluster-delete
spec:
  clusterConditions:
    - status: "True"
      type: ManagedClusterConditionAvailable
  clusterSelector:
    matchExpressions:
      - key: mykey
        operator: In
        values:
          - myvalue
    1 The policy-template spec.remediationAction is overridden by the preceding parameter value for spec.remediationAction.
    2 This namespace field must have the openshift-storage value.

  3. Set the value of the PlacementRule.spec.clusterSelector field to select the clusters from which to uninstall LVM Storage.

  4. Create the policy by running the following command:

    # oc create -f lvms-remove-policy.yaml -n lvms-policy-ns

  5. To create a policy to check if the LVMCluster CR has been removed, save the following YAML to a file with a name such as check-lvms-remove-policy.yaml:

    apiVersion: policy.open-cluster-management.io/v1
kind: Policy
metadata:
  name: policy-lvmcluster-inform
  annotations:
    policy.open-cluster-management.io/standards: NIST SP 800-53
    policy.open-cluster-management.io/categories: CM Configuration Management
    policy.open-cluster-management.io/controls: CM-2 Baseline Configuration
spec:
  remediationAction: inform
  disabled: false
  policy-templates:
    - objectDefinition:
        apiVersion: policy.open-cluster-management.io/v1
        kind: ConfigurationPolicy
        metadata:
          name: policy-lvmcluster-removal-inform
        spec:
          remediationAction: inform (1)
          severity: low
          object-templates:
            - complianceType: mustnothave
              objectDefinition:
                kind: LVMCluster
                apiVersion: lvm.topolvm.io/v1alpha1
                metadata:
                  name: my-lvmcluster
                  namespace: openshift-storage (2)
---
apiVersion: policy.open-cluster-management.io/v1
kind: PlacementBinding
metadata:
  name: binding-policy-lvmcluster-check
placementRef:
  apiGroup: apps.open-cluster-management.io
  kind: PlacementRule
  name: placement-policy-lvmcluster-check
subjects:
  - apiGroup: policy.open-cluster-management.io
    kind: Policy
    name: policy-lvmcluster-inform
---
apiVersion: apps.open-cluster-management.io/v1
kind: PlacementRule
metadata:
  name: placement-policy-lvmcluster-check
spec:
  clusterConditions:
    - status: "True"
      type: ManagedClusterConditionAvailable
  clusterSelector:
    matchExpressions:
      - key: mykey
        operator: In
        values:
          - myvalue
    1 The policy-template spec.remediationAction is overridden by the preceding parameter value for spec.remediationAction.
    2 The namespace field must have the openshift-storage value.

  6. Create the policy by running the following command:

    # oc create -f check-lvms-remove-policy.yaml -n lvms-policy-ns

  7. Check the policy status by running the following command:

    # oc get policy -n lvms-policy-ns
    Example output
    NAME                       REMEDIATION ACTION   COMPLIANCE STATE   AGE
policy-lvmcluster-delete   enforce              Compliant          15m
policy-lvmcluster-inform   inform               Compliant          15m

  8. After both the policies are compliant, save the following YAML to a file with a name such as lvms-uninstall-policy.yaml to create a policy to uninstall LVM Storage.

    apiVersion: apps.open-cluster-management.io/v1
kind: PlacementRule
metadata:
  name: placement-uninstall-lvms
spec:
  clusterConditions:
  - status: "True"
    type: ManagedClusterConditionAvailable
  clusterSelector:
    matchExpressions:
    - key: mykey
      operator: In
      values:
      - myvalue
---
apiVersion: policy.open-cluster-management.io/v1
kind: PlacementBinding
metadata:
  name: binding-uninstall-lvms
placementRef:
  apiGroup: apps.open-cluster-management.io
  kind: PlacementRule
  name: placement-uninstall-lvms
subjects:
- apiGroup: policy.open-cluster-management.io
  kind: Policy
  name: uninstall-lvms
---
apiVersion: policy.open-cluster-management.io/v1
kind: Policy
metadata:
  annotations:
    policy.open-cluster-management.io/categories: CM Configuration Management
    policy.open-cluster-management.io/controls: CM-2 Baseline Configuration
    policy.open-cluster-management.io/standards: NIST SP 800-53
  name: uninstall-lvms
spec:
  disabled: false
  policy-templates:
  - objectDefinition:
      apiVersion: policy.open-cluster-management.io/v1
      kind: ConfigurationPolicy
      metadata:
        name: uninstall-lvms
      spec:
        object-templates:
        - complianceType: mustnothave
          objectDefinition:
            apiVersion: v1
            kind: Namespace
            metadata:
              name: openshift-storage
        - complianceType: mustnothave
          objectDefinition:
            apiVersion: operators.coreos.com/v1
            kind: OperatorGroup
            metadata:
              name: openshift-storage-operatorgroup
              namespace: openshift-storage
            spec:
              targetNamespaces:
              - openshift-storage
        - complianceType: mustnothave
          objectDefinition:
            apiVersion: operators.coreos.com/v1alpha1
            kind: Subscription
            metadata:
              name: lvms-operator
              namespace: openshift-storage
        remediationAction: enforce
        severity: low
  - objectDefinition:
      apiVersion: policy.open-cluster-management.io/v1
      kind: ConfigurationPolicy
      metadata:
        name: policy-remove-lvms-crds
      spec:
        object-templates:
        - complianceType: mustnothave
          objectDefinition:
            apiVersion: apiextensions.k8s.io/v1
            kind: CustomResourceDefinition
            metadata:
              name: logicalvolumes.topolvm.io
        - complianceType: mustnothave
          objectDefinition:
            apiVersion: apiextensions.k8s.io/v1
            kind: CustomResourceDefinition
            metadata:
              name: lvmclusters.lvm.topolvm.io
        - complianceType: mustnothave
          objectDefinition:
            apiVersion: apiextensions.k8s.io/v1
            kind: CustomResourceDefinition
            metadata:
              name: lvmvolumegroupnodestatuses.lvm.topolvm.io
        - complianceType: mustnothave
          objectDefinition:
            apiVersion: apiextensions.k8s.io/v1
            kind: CustomResourceDefinition
            metadata:
              name: lvmvolumegroups.lvm.topolvm.io
        remediationAction: enforce
        severity: high

  9. Create the policy by running the following command:

    # oc create -f lvms-uninstall-policy.yaml -ns lvms-policy-ns
Additional resources

Limitations to configure the size of the devices used in LVM Storage

The limitations to configure the size of the devices that you can use to provision storage using LVM Storage are as follows:

  • The total storage size that you can provision is limited by the size of the underlying Logical Volume Manager (LVM) thin pool and the over-provisioning factor.

  • The size of the logical volume depends on the size of the Physical Extent (PE) and the Logical Extent (LE).

    • You can define the size of PE and LE during the physical and logical device creation.

    • The default PE and LE size is 4 MB.

    • If the size of the PE is increased, the maximum size of the LVM is determined by the kernel limits and your disk space.

Table 1. Size limits for different architectures using the default PE and LE size
Architecture RHEL 6 RHEL 7 RHEL 8 RHEL 9

32-bit

16 TB

-

-

-

64-bit

8 EB [1]

100 TB [2]

8 EB [1]

500 TB [2]

8 EB

8 EB

  1. Theoretical size.

  2. Tested size.

Creating Logical Volume Manager cluster

You can create a Logical Volume Manager cluster after you install LVM Storage.

OpenShift Container Platform supports additional worker nodes for single-node OpenShift clusters on bare-metal user-provisioned infrastructure. LVM Storage detects and uses the additional worker nodes when the new nodes show up. In case you need to set a node filter for the additional worker nodes, you can use the YAML view while creating the cluster.

You can only create a single instance of the LVMCluster custom resource (CR) on an OpenShift Container Platform cluster.

This node filter matching is not the same as the pod label matching.
Prerequisites

  • You installed LVM Storage from the OperatorHub.

Procedure

  1. In the OpenShift Container Platform Web Console, click Operators → Installed Operators to view all the installed Operators.

    Ensure that the Project selected is openshift-storage.

  2. Click on LVM Storage, and then click Create LVMCluster under LVMCluster.

  3. In the Create LVMCluster page, select either Form view or YAML view.

  4. Enter a name for the cluster.

  5. Click Create.

  6. Optional: To add a node filter, click YAML view and specify the filter in the nodeSelector section:

    apiVersion: lvm.topolvm.io/v1alpha1
kind: LVMCluster
metadata:
  name: my-lvmcluster
spec:
  storage:
    deviceClasses:
      - name: vg1
        thinPoolConfig:
          name: thin-pool-1
          sizePercent: 90
          overprovisionRatio: 10
        nodeSelector:
          nodeSelectorTerms:
            - matchExpressions:
              - key: app
                operator: In
                values:
                - test1

  7. Optional: To edit the local device path of the disks, click YAML view and specify the device path in the deviceSelector section:

    spec:
  storage:
    deviceClasses:
      - name: vg1
        deviceSelector:
          paths:
          - /dev/disk/by-path/pci-0000:87:00.0-nvme-1
          - /dev/disk/by-path/pci-0000:88:00.0-nvme-1
        thinPoolConfig:
          name: thin-pool-1
          sizePercent: 90
          overprovisionRatio: 10
Verification Steps

  1. Click Storage → Storage Classes from the left pane of the OpenShift Container Platform Web Console.

  2. Verify that the lvms-<device-class-name> storage class is created with the LVMCluster creation. By default, vg1 is the device-class-name.

Additional resources

Provisioning storage using LVM Storage

You can provision persistent volume claims (PVCs) using the storage class that is created during the Operator installation. You can provision block and file PVCs, however, the storage is allocated only when a pod that uses the PVC is created.

LVM Storage provisions PVCs in units of 1 GiB. The requested storage is rounded up to the nearest GiB.
Procedure

  1. Identify the StorageClass that is created when LVM Storage is deployed.

    The StorageClass name is in the format, lvms-<device-class-name>. The device-class-name is the name of the device class that you provided in the LVMCluster of the Policy YAML. For example, if the deviceClass is called vg1, then the storageClass name is lvms-vg1.

    The volumeBindingMode of the storage class is set to WaitForFirstConsumer.

  2. To create a PVC where the application requires storage, save the following YAML to a file with a name such as pvc.yaml.

    Example YAML to create a PVC
    # block pvc
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: lvm-block-1
  namespace: default
spec:
  accessModes:
    - ReadWriteOnce
  volumeMode: Block
  resources:
    requests:
      storage: 10Gi
  storageClassName: lvms-vg1
---
# file pvc
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: lvm-file-1
  namespace: default
spec:
  accessModes:
    - ReadWriteOnce
  volumeMode: Filesystem
  resources:
    requests:
      storage: 10Gi
  storageClassName: lvms-vg1

  3. Create the PVC by running the following command:

    # oc create -f pvc.yaml -ns <application_namespace>

    The created PVCs remain in pending state until you deploy the pods that use them.

Scaling storage of single-node OpenShift clusters

The OpenShift Container Platform supports additional worker nodes for single-node OpenShift clusters on bare-metal user-provisioned infrastructure. LVM Storage detects and uses the new additional worker nodes when the nodes show up.

Additional resources

Scaling up storage by adding capacity to your single-node OpenShift cluster

To scale the storage capacity of your configured worker nodes on a single-node OpenShift cluster, you can increase the capacity by adding disks.

Prerequisites

  • You have additional unused disks on each single-node OpenShift cluster to be used by LVM Storage.

Procedure

  1. Log in to OpenShift Container Platform console of the single-node OpenShift cluster.

  2. From the Operators → Installed Operators page, click on the LVM Storage Operator in the openshift-storage namespace.

  3. Click on the LVMCluster tab to list the LVMCluster CR created on the cluster.

  4. Select Edit LVMCluster from the Actions drop-down menu.

  5. Click on the YAML tab.

  6. Edit the LVMCluster CR YAML to add the new device path in the deviceSelector section:

    In case the deviceSelector field is not included during the LVMCluster creation, it is not possible to add the deviceSelector section to the CR. You need to remove the LVMCluster and then create a new CR.

    		 
    apiVersion: lvm.topolvm.io/v1alpha1
kind: LVMCluster
metadata:
  name: my-lvmcluster
spec:
  storage:
    deviceClasses:
    - name: vg1
      deviceSelector:
        paths:
        - /dev/disk/by-path/pci-0000:87:00.0-nvme-1 (1)
        - /dev/disk/by-path/pci-0000:88:00.0-nvme-1
        - /dev/disk/by-path/pci-0000:89:00.0-nvme-1 (2)
      thinPoolConfig:
        name: thin-pool-1
        sizePercent: 90
        overprovisionRatio: 10
    1 The path can be added by name (/dev/sdb) or by path.
    2 A new disk is added.
Additional resources

Scaling up storage by adding capacity to your single-node OpenShift cluster using RHACM

You can scale the storage capacity of your configured worker nodes on a single-node OpenShift cluster using RHACM.

Prerequisites

  • You have access to the RHACM cluster using an account with cluster-admin privilages.

  • You have additional unused disks on each single-node OpenShift cluster to be used by LVM Storage.

Procedure

  1. Log in to the RHACM CLI using your OpenShift Container Platform credentials.

  2. Find the disk that you want to add. The disk to be added needs to match with the device name and path of the existing disks.

  3. To add capacity to the single-node OpenShift cluster, edit the deviceSelector section of the existing policy YAML, for example, policy-lvms-operator.yaml.

    In case the deviceSelector field is not included during the LVMCluster creation, it is not possible to add the deviceSelector section to the CR. You need to remove the LVMCluster and then recreate from the new CR.

    		 
    apiVersion: apps.open-cluster-management.io/v1
kind: PlacementRule
metadata:
  name: placement-install-lvms
spec:
  clusterConditions:
  - status: "True"
    type: ManagedClusterConditionAvailable
  clusterSelector:
    matchExpressions:
    - key: mykey
      operator: In
      values:
      - myvalue
---
apiVersion: policy.open-cluster-management.io/v1
kind: PlacementBinding
metadata:
  name: binding-install-lvms
placementRef:
  apiGroup: apps.open-cluster-management.io
  kind: PlacementRule
  name: placement-install-lvms
subjects:
- apiGroup: policy.open-cluster-management.io
  kind: Policy
  name: install-lvms
---
apiVersion: policy.open-cluster-management.io/v1
kind: Policy
metadata:
  annotations:
    policy.open-cluster-management.io/categories: CM Configuration Management
    policy.open-cluster-management.io/controls: CM-2 Baseline Configuration
    policy.open-cluster-management.io/standards: NIST SP 800-53
  name: install-lvms
spec:
  disabled: false
  remediationAction: enforce
  policy-templates:
  - objectDefinition:
      apiVersion: policy.open-cluster-management.io/v1
      kind: ConfigurationPolicy
      metadata:
        name: install-lvms
      spec:
        object-templates:
        - complianceType: musthave
          objectDefinition:
            apiVersion: v1
            kind: Namespace
            metadata:
              labels:
                openshift.io/cluster-monitoring: "true"
                pod-security.kubernetes.io/enforce: privileged
                pod-security.kubernetes.io/audit: privileged
                pod-security.kubernetes.io/warn: privileged
              name: openshift-storage
        - complianceType: musthave
          objectDefinition:
            apiVersion: operators.coreos.com/v1
            kind: OperatorGroup
            metadata:
              name: openshift-storage-operatorgroup
              namespace: openshift-storage
            spec:
              targetNamespaces:
              - openshift-storage
        - complianceType: musthave
          objectDefinition:
            apiVersion: operators.coreos.com/v1alpha1
            kind: Subscription
            metadata:
              name: lvms
              namespace: openshift-storage
            spec:
              installPlanApproval: Automatic
              name: lvms-operator
              source: redhat-operators
              sourceNamespace: openshift-marketplace
        remediationAction: enforce
        severity: low
  - objectDefinition:
      apiVersion: policy.open-cluster-management.io/v1
      kind: ConfigurationPolicy
      metadata:
        name: lvms
      spec:
        object-templates:
           - complianceType: musthave
             objectDefinition:
               apiVersion: lvm.topolvm.io/v1alpha1
               kind: LVMCluster
               metadata:
                 name: my-lvmcluster
                 namespace: openshift-storage
               spec:
                 storage:
                   deviceClasses:
                   - name: vg1
                     deviceSelector:
                       paths:
                       - /dev/disk/by-path/pci-0000:87:00.0-nvme-1
                       - /dev/disk/by-path/pci-0000:88:00.0-nvme-1
                       - /dev/disk/by-path/pci-0000:89:00.0-nvme-1 # new disk is added
                     thinPoolConfig:
                       name: thin-pool-1
                       sizePercent: 90
                       overprovisionRatio: 10
                     nodeSelector:
                       nodeSelectorTerms:
                       - matchExpressions:
                           - key: app
                             operator: In
                             values:
                             - test1
        remediationAction: enforce
        severity: low

  4. Edit the policy by running the following command:

    # oc edit -f policy-lvms-operator.yaml -ns lvms-policy-ns (1)
    1 The policy-lvms-operator.yaml is the name of the existing policy.

    This uses the new disk specified in the LVMCluster CR to provision storage.

Additional resources

Expanding PVCs

To leverage the new storage after adding additional capacity, you can expand existing persistent volume claims (PVCs) with LVM Storage.

Prerequisites

  • Dynamic provisioning is used.

  • The controlling StorageClass object has allowVolumeExpansion set to true.

Procedure

  1. Modify the .spec.resources.requests.storage field in the desired PVC resource to the new size by running the following command:

    oc patch <pvc_name> -n <application_namespace> -p '{ "spec": { "resources": { "requests": { "storage": "<desired_size>" }}}}'

  2. Watch the status.conditions field of the PVC to see if the resize has completed. OpenShift Container Platform adds the Resizing condition to the PVC during expansion, which is removed after the expansion completes.

Additional resources

Upgrading LVM Storage on single-node OpenShift clusters

Currently, it is not possible to upgrade from OpenShift Data Foundation Logical Volume Manager Operator 4.11 to LVM Storage 4.12 on single-node OpenShift clusters.

The data will not be preserved during this process.
Procedure

  1. Back up any data that you want to preserve on the persistent volume claims (PVCs).

  2. Delete all PVCs provisioned by the OpenShift Data Foundation Logical Volume Manager Operator and their pods.

  3. Reinstall LVM Storage on OpenShift Container Platform 4.12.

  4. Recreate the workloads.

  5. Copy the backup data to the PVCs created after upgrading to 4.12.

Volume snapshots for single-node OpenShift

You can take volume snapshots of persistent volumes (PVs) that are provisioned by LVM Storage. You can also create volume snapshots of the cloned volumes. Volume snapshots help you to do the following:

  • Back up your application data.

    Volume snapshots are located on the same devices as the original data. To use the volume snapshots as backups, you need to move the snapshots to a secure location. You can use OpenShift API for Data Protection backup and restore solutions.

  • Revert to a state at which the volume snapshot was taken.

Additional resources

Creating volume snapshots in single-node OpenShift

You can create volume snapshots based on the available capacity of the thin pool and the overprovisioning limits. LVM Storage creates a VolumeSnapshotClass with the lvms-<deviceclass-name> name.

Prerequisites

  • You ensured that the persistent volume claim (PVC) is in Bound state. This is required for a consistent snapshot.

  • You stopped all the I/O to the PVC before taking the snapshot.

Procedure

  1. Log in to the single-node OpenShift for which you need to run the oc command.

  2. Save the following YAML to a file with a name such as lvms-vol-snapshot.yaml.

    Example YAML to create a volume snapshot
    apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
    name: lvm-block-1-snap
spec:
    volumeSnapshotClassName: lvms-vg1
    source:
        persistentVolumeClaimName: lvm-block-1

  3. Create the snapshot by running the following command in the same namespace as the PVC:

    # oc create -f lvms-vol-snapshot.yaml

A read-only copy of the PVC is created as a volume snapshot.

Restoring volume snapshots in single-node OpenShift

When you restore a volume snapshot, a new persistent volume claim (PVC) is created. The restored PVC is independent of the volume snapshot and the source PVC.

Prerequisites

  • The storage class must be the same as that of the source PVC.

  • The size of the requested PVC must be the same as that of the source volume of the snapshot.

    A snapshot must be restored to a PVC of the same size as the source volume of the snapshot. If a larger PVC is required, you can resize the PVC after the snapshot is restored successfully.
Procedure

  1. Identify the storage class name of the source PVC and volume snapshot name.

  2. Save the following YAML to a file with a name such as lvms-vol-restore.yaml to restore the snapshot.

    Example YAML to restore a PVC.
    kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: lvm-block-1-restore
spec:
  accessModes:
  - ReadWriteOnce
  volumeMode: Block
  Resources:
    Requests:
      storage: 2Gi
  storageClassName: lvms-vg1
  dataSource:
    name: lvm-block-1-snap
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io

  3. Create the policy by running the following command in the same namespace as the snapshot:

    # oc create -f lvms-vol-restore.yaml

Deleting volume snapshots in single-node OpenShift

You can delete volume snapshots resources and persistent volume claims (PVCs).

Procedure

  1. Delete the volume snapshot resource by running the following command:

    # oc delete volumesnapshot <volume_snapshot_name> -n <namespace>

    When you delete a persistent volume claim (PVC), the snapshots of the PVC are not deleted.

  2. To delete the restored volume snapshot, delete the PVC that was created to restore the volume snapshot by running the following command:

    # oc delete pvc <pvc_name> -n <namespace>

Volume cloning for single-node OpenShift

A clone is a duplicate of an existing storage volume that can be used like any standard volume.

Creating volume clones in single-node OpenShift

You create a clone of a volume to make a point-in-time copy of the data. A persistent volume claim (PVC) cannot be cloned with a different size.

The cloned PVC has write access.
Prerequisites

  • You ensured that the PVC is in Bound state. This is required for a consistent snapshot.

  • You ensured that the StorageClass is the same as that of the source PVC.

Procedure

  1. Identify the storage class of the source PVC.

  2. To create a volume clone, save the following YAML to a file with a name such as lvms-vol-clone.yaml:

    Example YAML to clone a volume
    apiVersion: v1
kind: PersistentVolumeClaim
Metadata:
  name: lvm-block-1-clone
Spec:
  storageClassName: lvms-vg1
  dataSource:
    name: lvm-block-1
    kind: PersistentVolumeClaim
  accessModes:
   - ReadWriteOnce
  volumeMode: Block
  Resources:
    Requests:
      storage: 2Gi

  3. Create the policy in the same namespace as the source PVC by running the following command:

    # oc create -f lvms-vol-clone.yaml

Deleting cloned volumes in single-node OpenShift

You can delete cloned volumes.

Procedure

  • To delete the cloned volume, delete the cloned PVC by running the following command:

    # oc delete pvc <clone_pvc_name> -n <namespace>

Monitoring LVM Storage

To enable cluster monitoring, you must add the following label in the namespace where you have installed LVM Storage:

openshift.io/cluster-monitoring=true

For information about enabling cluster monitoring in RHACM, see Observability and Adding custom metrics.

Metrics

You can monitor LVM Storage by viewing the metrics.

The following table describes the topolvm metrics:

Table 2. topolvm metrics
Alert Description

topolvm_thinpool_data_percent

Indicates the percentage of data space used in the LVM thinpool.

topolvm_thinpool_metadata_percent

Indicates the percentage of metadata space used in the LVM thinpool.

topolvm_thinpool_size_bytes

Indicates the size of the LVM thin pool in bytes.

topolvm_volumegroup_available_bytes

Indicates the available space in the LVM volume group in bytes.

topolvm_volumegroup_size_bytes

Indicates the size of the LVM volume group in bytes.

topolvm_thinpool_overprovisioned_available

Indicates the available over-provisioned size of the LVM thin pool in bytes.

Metrics are updated every 10 minutes or when there is a change, such as a new logical volume creation, in the thin pool.

Alerts

When the thin pool and volume group reach maximum storage capacity, further operations fail. This can lead to data loss.

LVM Storage sends the following alerts when the usage of the thin pool and volume group exceeds a certain value:

Table 3. LVM Storage alerts
Alert Description

VolumeGroupUsageAtThresholdNearFull

This alert is triggered when both the volume group and thin pool usage exceeds 75% on nodes. Data deletion or volume group expansion is required.

VolumeGroupUsageAtThresholdCritical

This alert is triggered when both the volume group and thin pool usage exceeds 85% on nodes. In this case, the volume group is critically full. Data deletion or volume group expansion is required.

ThinPoolDataUsageAtThresholdNearFull

This alert is triggered when the thin pool data uusage in the volume group exceeds 75% on nodes. Data deletion or thin pool expansion is required.

ThinPoolDataUsageAtThresholdCritical

This alert is triggered when the thin pool data usage in the volume group exceeds 85% on nodes. Data deletion or thin pool expansion is required.

ThinPoolMetaDataUsageAtThresholdNearFull

This alert is triggered when the thin pool metadata usage in the volume group exceeds 75% on nodes. Data deletion or thin pool expansion is required.

ThinPoolMetaDataUsageAtThresholdCritical

This alert is triggered when the thin pool metadata usage in the volume group exceeds 85% on nodes. Data deletion or thin pool expansion is required.

Downloading log files and diagnostic information using must-gather

When LVM Storage is unable to automatically resolve a problem, use the must-gather tool to collect the log files and diagnostic information so that you or the Red Hat Support can review the problem and determine a solution.

Procedure

  • Run the must-gather command from the client connected to the LVM Storage cluster:

    $ oc adm must-gather --image=registry.redhat.io/lvms4/lvms-must-gather-rhel9:v4.12 --dest-dir=<directory_name>
Additional resources

LVM Storage reference YAML file

The sample LVMCluster custom resource (CR) describes all the fields in the YAML file.

Example LVMCluster CR
apiVersion: lvm.topolvm.io/v1alpha1
kind: LVMCluster
metadata:
  name: my-lvmcluster
spec:
  tolerations:
  - effect: NoSchedule
    key: xyz
    operator: Equal
    value: "true"
  storage:
    deviceClasses: (1)
    - name: vg1  (2)
      nodeSelector: (3)
        nodeSelectorTerms: (4)
        - matchExpressions:
          - key: mykey
            operator: In
            values:
            - ssd
      deviceSelector: (5)
        paths:
        - /dev/disk/by-path/pci-0000:87:00.0-nvme-1
        - /dev/disk/by-path/pci-0000:88:00.0-nvme-1
        - /dev/disk/by-path/pci-0000:89:00.0-nvme-1
      thinPoolConfig: (6)
        name: thin-pool-1 (7)
        sizePercent: 90 (8)
        overprovisionRatio: 10 (9)
status:
    deviceClassStatuses: (10)
    - name: vg1
      nodeStatus: (11)
      - devices: (12)
        - /dev/nvme0n1
        - /dev/nvme1n1
        - /dev/nvme2n1
        node: my-node.example.com (13)
        status: Ready (14)
    ready: true (15)
    state: Ready (16)
1 The LVM volume groups to be created on the cluster. You can create only a single deviceClass.
2 The name of the LVM volume group to be created on the nodes.
3 The nodes on which to create the LVM volume group. If the field is empty, all nodes are considered.
4 A list of node selector requirements.
5 A list of device paths which is used to create the LVM volume group. If this field is empty, all unused disks on the node are used. After a device is added to the LVM volume volume group, it cannot be removed.
6 The LVM thin pool configuration.
7 The name of the thin pool to be created in the LVM volume group.
8 The percentage of remaining space in the LVM volume group that should be used for creating the thin pool.
9 The factor by which additional storage can be provisioned compared to the available storage in the thin pool.
10 The status of the deviceClass.
11 The status of the LVM volume group on each node.
12 The list of devices used to create the LVM volume group.
13 The node on which the deviceClass was created.
14 The status of the LVM volume group on the node.
15 This field is deprecated.
16 The status of the LVMCluster.