Creating a StorageClass with topology awareness

When using the CSI Topology feature, different parameters must be taken into account when creating a storage class YAML file with specific by_management_id requirements. Use this information to help define a StorageClass that is topology aware.

For information and parameter definitions that are not related to topology awareness, be sure to see the information provided in Creating a StorageClass, in addition to the current section.

The StorageClass file must be defined to contain topology information, based off of the labels that were already defined on the nodes in the cluster (see Compatibility and requirements). This determines the storage pools that are then served as candidates for PersistentVolumeClaim (PVC) requests made, as well as the subset of nodes that can make use of the volumes provisioned by the CSI driver.

With topology awareness, the StorageClass must have the volumeBindingMode set to WaitForFirstConsumer (as defined in the .yaml example below). This defines that any PVCs that are requested with this specific StorageClass, will wait to be configured until the CSI driver can see the worker node topology.

The by_management_id parameter is optional and values such as the pool, SpaceEfficiency, and volume_name_prefix may all be specified.

The various by_management_id parameters are chosen within the following hierarchical order:

1. From within the by_management_id parameter, per system (if specified).

2. Outside of the parameter, as a cross-system default (if not specified within the by_management_id parameter for the relevant management-id).

    kind: StorageClass
    apiVersion: storage.k8s.io/v1
    metadata:
      name: demo-storageclass-config-secret
    provisioner: block.csi.ibm.com
    volumeBindingMode: WaitForFirstConsumer
    parameters:
      # non-csi.storage.k8s.io parameters may be specified in by_management_id per system and/or outside by_management_id as the cross-system default.
   
      by_management_id: '{"demo-management-id-1":{"pool":"demo-pool-1","SpaceEfficiency":"dedup_compressed","volume_name_prefix":"demo-prefix-1"},
                          "demo-management-id-2":{"pool":"demo-pool-2","volume_name_prefix":"demo-prefix-2", "io_group": "demo-iogrp"}}'  # Optional.
      pool: demo-pool
      SpaceEfficiency: thin            # Optional.
      volume_name_prefix: demo-prefix  # Optional.
   
      csi.storage.k8s.io/fstype: xfs   # Optional. Values ext4/xfs. The default is ext4.
      csi.storage.k8s.io/secret-name: demo-config-secret
      csi.storage.k8s.io/secret-namespace: default
    allowVolumeExpansion: true
   

Apply the storage class.

kubectl apply -f <filename>.yaml

The storageclass.storage.k8s.io/<storageclass-name> created message is emitted.