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Chapter 4. Scaling storage of bare metal OpenShift Data Foundation cluster

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To scale the storage capacity of your configured Red Hat OpenShift Data Foundation worker nodes on your bare metal cluster, you can increase the capacity by adding three disks at a time. Three disks are needed since OpenShift Data Foundation uses a replica count of 3 to maintain the high availability. So the amount of storage consumed is three times the usable space.

Note

Usable space may vary when encryption is enabled or replica 2 pools are being used.

4.1. Scaling up a cluster created using local storage devices

In order to scale up an OpenShift Data Foundation cluster which was created using local storage devices, a new disk needs to be added to the storage node. It is recommended to have the new disks of the same size as used earlier during the deployment as OpenShift Data Foundation does not support heterogeneous disks/OSD’s.

For deployments having three failure domains, you can scale up the storage by adding disks in the multiple of three, with the same number of disks coming from nodes in each of the failure domains. For example, if we scale by adding six disks, two disks are taken from nodes in each of the three failure domains. If the number of disks is not in multiples of three, it will only consume the disk to the maximum in the multiple of three while the remaining disks remain unused.

For deployments having less than three failure domains, there is flexibility in adding the number of disks. In this case, you can add any number of disks. In order to check if flexible scaling is enabled or not, refer to the Knowledgebase article Verify if flexible scaling is enabled.

Note

Flexible scaling features get enabled at the time of deployment and can not be enabled or disabled later on.

Prerequisites

  • You have administrative privilege to the OpenShift Container Platform Console.
  • You have a running OpenShift Data Foundation Storage Cluster.
  • Disks to be used for scaling are already attached to the storage node
  • LocalVolumeDiscovery and LocalVolumeSet objects are already created.

Procedure

To add capacity, you can either use a storage class that you provisioned during the deployment or any other storage class that matches the filter.

  1. In the OpenShift Web Console, click Operators Installed Operators.
  2. Click OpenShift Data Foundation Operator.

  3. Click Storage Systems tab.

    1. Click the Action menu (⋮) next to the visible list to extend the options menu.
    2. Select Add Capacity from the options menu.
    3. Select the Storage Class for which you added disks or the new storage class depending on your requirement. Available Capacity displayed is based on the local disks available in storage class.
    4. Click Add.
  4. To check the status, navigate to Storage Data Foundation and verify that the Storage System in the Status card has a green tick.

Verification steps

  • Verify the Raw Capacity card.

    1. In the OpenShift Web Console, click Storage Data Foundation.
    2. In the Status card of the Overview tab, click Storage System and then click the storage system link from the pop up that appears.

    3. In the Block and File tab, check the Raw Capacity card.

      Note that the capacity increases based on your selections.

      Note

      The raw capacity does not take replication into account and shows the full capacity.

  • Verify that the new OSDs and their corresponding new Persistent Volume Claims (PVCs) are created.

    • To view the state of the newly created OSDs:

      1. Click Workloads Pods from the OpenShift Web Console.

      2. Select openshift-storage from the Project drop-down list.

        Note

        If the Show default projects option is disabled, use the toggle button to list all the default projects.

    • To view the state of the PVCs:

      1. Click Storage Persistent Volume Claims from the OpenShift Web Console.

      2. Select openshift-storage from the Project drop-down list.

        Note

        If the Show default projects option is disabled, use the toggle button to list all the default projects.

  • Optional: If cluster-wide encryption is enabled on the cluster, verify that the new OSD devices are encrypted.

    1. Identify the nodes where the new OSD pods are running. 

      $ oc get -n openshift-storage -o=custom-columns=NODE:.spec.nodeName pod/<OSD-pod-name>
      <OSD-pod-name>

      Is the name of the OSD pod.

      For example: 

      $ oc get -n openshift-storage -o=custom-columns=NODE:.spec.nodeName pod/rook-ceph-osd-0-544db49d7f-qrgqm

      Example output: 

      NODE
compute-1

    2. For each of the nodes identified in the previous step, do the following:

      1. Create a debug pod and open a chroot environment for the selected host(s). 

        $ oc debug node/<node-name>
        <node-name>

        Is the name of the node. 

        $ chroot /host

      2. Check for the crypt keyword beside the ocs-deviceset names. 

        $ lsblk
Important

Cluster reduction is supported only with the Red Hat Support Team’s assistance.

4.2. Scaling out storage capacity on a bare metal cluster

OpenShift Data Foundation is highly scalable. It can be scaled out by adding new nodes with required storage and enough hardware resources in terms of CPU and RAM. There is no limit on the number of nodes which can be added. Howerver, from the technical support perspective, 2000 nodes is the limit for OpenShift Data Foundation.

Scaling out storage capacity can be broken down into two steps

  • Adding new node using local storage device
  • Scaling up the storage capacity
Note

OpenShift Data Foundation does not support heterogeneous OSD/Disk sizes.

4.2.1. Adding a node using a local storage device

You can add nodes to increase the storage capacity when existing worker nodes are already running at their maximum supported OSDs or when there are not enough resources to add new OSDs on the existing nodes.

Add nodes in the multiple of 3, each of them in different failure domains. Though it is recommended to add nodes in multiples of 3 nodes, you have the flexibility to add one node at a time in flexible scaling deployment. See Knowledgebase article Verify if flexible scaling is enabled

Note

OpenShift Data Foundation does not support heterogeneous disk size and types. The new nodes to be added should have the disk of the same type and size which was used during initial OpenShift Data Foundation deployment.

Prerequisites

  • You have administrative privilege to the OpenShift Container Platform Console.
  • You have a running OpenShift Data Foundation Storage Cluster.

Procedure

  1. Depending on the type of infrastructure, perform the following steps:

    1. Get a new machine with the required infrastructure. See Platform requirements.
    2. Create a new OpenShift Container Platform worker node using the new machine.

  2. Check for certificate signing requests (CSRs) that are in Pending state. 

    $ oc get csr

  3. Approve all the required CSRs for the new node. 

    $ oc adm certificate approve <Certificate_Name>
    <Certificate_Name>
    Is the name of the CSR.
  4. Click Compute Nodes, confirm if the new node is in Ready state.

  5. Apply the OpenShift Data Foundation label to the new node using any one of the following:

    From User interface
    1. For the new node, click Action Menu (⋮) Edit Labels.
    2. Add cluster.ocs.openshift.io/openshift-storage, and click Save.
    From Command line interface

    • Apply the OpenShift Data Foundation label to the new node. 

      $ oc label node <new_node_name> cluster.ocs.openshift.io/openshift-storage=""
      <new_node_name>
      Is the name of the new node.

  6. Click Operators Installed Operators from the OpenShift Web Console.

    From the Project drop-down list, make sure to select the project where the Local Storage Operator is installed.

  7. Click Local Storage.

  8. Click the Local Volume Discovery tab.

    1. Beside the LocalVolumeDiscovery, click Action menu (⋮) Edit Local Volume Discovery.
    2. In the YAML, add the hostname of the new node in the values field under the node selector.
    3. Click Save.

  9. Click the Local Volume Sets tab.

    1. Beside the LocalVolumeSet, click Action menu (⋮) Edit Local Volume Set.

    2. In the YAML, add the hostname of the new node in the values field under the node selector.

      Figure 4.1. YAML showing the addition of new hostnames

      Screenshot of YAML showing the addition of new hostnames.
    3. Click Save.
Note

It is recommended to add 3 nodes, one each in different zones. You must add 3 nodes and perform this procedure for all of them.

Verification steps

  1. Execute the following command the terminal and verify that the new node is present in the output: 

    $ oc get nodes --show-labels | grep cluster.ocs.openshift.io/openshift-storage= |cut -d' ' -f1

  2. On the OpenShift web console, click Workloads Pods, confirm that at least the following pods on the new node are in Running state:

    • csi-cephfsplugin-*
    • csi-rbdplugin-*

4.2.2. Scaling up storage capacity

To scale up storage capacity, see Scaling up storage by adding capacity.

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