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The Container Storage Interface is based on a specification that is maintained by the CNCF, to provide features above and beyond what are covered by the CSI specification Dell has released a collection of Container Storage Modules (CSM). Some of the modules that may be of particular interest for APEX Cloud Platform users are:
- Resiliency Module – provides faster failover for pods that use Persistent Volumes.
To protect the integrity of the data within the Persistent Volume, when a node fails the pod will not be scheduled on a new node until an admin confirms the node is no longer running and not writing to the volume. This is known as “Non-graceful node shutdown” scenario. The resiliency module uses the API of the underlying Dell SDS to immediately identify a node failure and confirm that no data is being written to the volume, and automatically marks the pod as schedulable without any manual tasks. This greatly minimizes the time needed for a pod to recover in the event of a node failure.
The module works with allow-list, every Pod with the label podmon.dellemc.com/driver:csi-vxflexos are protected.
- Observability Module – provides storage metrics into Kubernetes that can be used to identify storage usage and performance down to the pod level.
Kubernetes allows storage providers to expose simple capacity metrics to kube-stat. This is achieved natively in the CSI driver and allows all persistent volumes in APEX Cloud Platform to be visible in the OpenShift UI and OpenShift Monitoring.
The Observability module uses OpenTelemetry to capture performance metrics and topology from the storage cluster and makes them available in a Prometheus database. The module also includes standard Grafana dashboards that allow easy access to performance and storage cluster data like:
Note: OpenShift monitoring forbids adding external metrics to its Prometheus instance. To visualize the metrics, deploying or connecting to a separate Prometheus/Grafana stack is necessary.
This is not an extensive list of the Dell Container Storage Modules. For more information, see https://dell.github.io/csm-docs/docs/.