Limiting Storage Consumption
This example demonstrates an easy way to limit the amount of storage consumed in a namespace.
The following resources are used in the demonstration:
This example assumes you have a functional Kubernetes setup.
Limiting Storage Consumption
The cluster-admin is operating a cluster on behalf of a user population and the admin wants to control how much storage a single namespace can consume in order to control cost.
The admin would like to limit:
- The number of persistent volume claims in a namespace
- The amount of storage each claim can request
- The amount of cumulative storage the namespace can have
LimitRange to limit requests for storage
Adding a LimitRange to a namespace enforces storage request sizes to a minimum and maximum. Storage is requested
via PersistentVolumeClaim. The admission controller that enforces limit ranges will reject any PVC that is above or below
the values set by the admin.
In this example, a PVC requesting 10Gi of storage would be rejected because it exceeds the 2Gi max.
apiVersion: v1
kind: LimitRange
metadata:
name: storagelimits
spec:
limits:
- type: PersistentVolumeClaim
max:
storage: 2Gi
min:
storage: 1Gi
Minimum storage requests are used when the underlying storage provider requires certain minimums. For example, AWS EBS volumes have a 1Gi minimum requirement.
StorageQuota to limit PVC count and cumulative storage capacity
Admins can limit the number of PVCs in a namespace as well as the cumulative capacity of those PVCs. New PVCs that exceed either maximum value will be rejected.
In this example, a 6th PVC in the namespace would be rejected because it exceeds the maximum count of 5. Alternatively, a 5Gi maximum quota when combined with the 2Gi max limit above, cannot have 3 PVCs where each has 2Gi. That would be 6Gi requested for a namespace capped at 5Gi.
apiVersion: v1
kind: ResourceQuota
metadata:
name: storagequota
spec:
hard:
persistentvolumeclaims: "5"
requests.storage: "5Gi"
Summary
A limit range can put a ceiling on how much storage is requested while a resource quota can effectively cap the storage consumed by a namespace through claim counts and cumulative storage capacity. The allows a cluster-admin to plan their cluster’s storage budget without risk of any one project going over their allotment.