CSIStorageCapacity stores the result of one CSI GetCapacity call. For a given StorageClass, this describes the available capacity in a particular topology segment. This can be used when considering where to instantiate new PersistentVolumes.

For example this can express things like: - StorageClass "standard" has "1234 GiB" available in "topology.kubernetes.io/zone=us-east1" - StorageClass "localssd" has "10 GiB" available in "kubernetes.io/hostname=knode-abc123"

The following three cases all imply that no capacity is available for a certain combination: - no object exists with suitable topology and storage class name - such an object exists, but the capacity is unset - such an object exists, but the capacity is zero

The producer of these objects can decide which approach is more suitable.

They are consumed by the kube-scheduler when a CSI driver opts into capacity-aware scheduling with CSIDriverSpec.StorageCapacity. The scheduler compares the MaximumVolumeSize against the requested size of pending volumes to filter out unsuitable nodes. If MaximumVolumeSize is unset, it falls back to a comparison against the less precise Capacity. If that is also unset, the scheduler assumes that capacity is insufficient and tries some other node.