volume-placement-strategies-crd-reference

Portworx provides a CustomResouceDefinition (CRD) called VolumePlacementStrategy. The specification for this CRD is composed of 4 main sections:

• replicaAffinity
  • Schema
  • Example use cases
• replicaAntiAffinity
  • Schema
  • Example use cases
• volumeAffinity
  • Schema
  • Example use cases
• volumeAntiAffinity
  • Schema
  • Example use cases

Additional Information:

• topologyKey
• Templates

replicaAffinity

Schema

Example use cases of replicaAffinity

• Use SSD pools
• Use SSD and SATA and spread replicas evenly
• First replica SSD, others SATA
• Place volume on specific nodes, example infra etc
• Place volume only on racks 1, 2 and 3

By default, Portworx automatically adds the following labels to each of its storage pools. These can be used for replica affinity rules to target replicas on a specific storage pool type:

• iopriority
• medium (Media Type)

replicaAntiAffinity

Schema

Example use cases

• Antiaffinity to data pools and spread across racks
• Antiaffinity to not use SATA pools

volumeAffinity

Schema

Example use cases

• Collocate postgres volumes
• Place volume on DB type nodes or collocate with postgres volumes

volumeAntiAffinity

Schema

Example use cases

Do not collocate with other cassandra volumes

topologyKey

If topologyKey is not set, by default the rule will avoid/colocate volumes at the node level using built-in unique node identifiers.

Portworx Built-in

topologyKey can use the built-in key portworx.io/pool that is set automatically as a unique key/value on every Portworx pool. This can be used with volumeAffinity/volumeAntiAffinity to control volume placement at the pool level to work for individual pools.

Templates

Parameter values in matchExpressions may use predefined templates. The VolumePlacementStrategy will automatically resolve these templates at provision time as detailed below:

• key: namespace
  • ${pvc.namespace}
    • Replaced with namespace of the PersistentVolumeClaim that triggered provisioning
    • Example: Do not collocate with other app volumes within the same namespace
• key: px/statefulset-pod
  • ${pvc.statefulset-pod}
    • Replaced with the StatefulSet pod name the PersistentVolumeClaim belongs to
    • Matches corresponding label key/value applied to the volume
    • Use this with multiple volumeClaimTemplates in a StatefulSet to relate volumes for the same replica pod to each other
    • Works with Immediate binding mode
    • Example: Collocate volumes that belong to the same StatefulSet pod
• key: labelkey
  • ${pvc.labels.labelkey}
    • Portworx replaces any values in the template ${pvc.labels.labelkey} with the pvc.labels value for labelkey.
    • Example: Label the volumes dynamically based on the PVC label field