Storage Capacity Tracking

Status

Overview

Storage capacity tracking allows the Kubernetes scheduler to make more informed choices about where to start pods which depend on unbound volumes with late binding (aka "wait for first consumer"). Without storage capacity tracking, a node is chosen without knowing whether those volumes can be made available for the node. Volume creation is attempted and if that fails, the pod has to be rescheduled, potentially landing on the same node again. With storage capacity tracking, the scheduler filters out nodes which do not have enough capacity.

For design information, see the enhancement proposal.

Usage

To support rescheduling of a pod, a CSI driver deployment must:

• return the ResourceExhausted gRPC status code in CreateVolume if capacity is exhausted
• use external-provisioner >= 1.6.0 because older releases did not properly support rescheduling after a ResourceExhausted error

To support storage capacity tracking, a CSI driver deployment must:

• implement the GetCapacity call
• use external-provisioner >= 2.0.0
• enable producing of storage capacity objects as explained in the external-provisioner documentation
• enable usage of that information by setting the CSIDriverSpec.StorageCapacity field to True
• run on a cluster where the storage capacity API is enabled

Further information can be found in the Kubernetes documentation.