Pod placement rules
Kubernetes is responsible for pod placement based on declarative placement rules.
The IBM Storage Fusion
Data Foundation base service placement rules for
Internal cluster can be summarized as follows:
- Nodes are labeled with the
cluster.ocs.openshift.io/openshift-storagekey. - Nodes are sorted into pseudo failure domains if none exist.
- Components requiring high availability are spread across failure domains.
- A storage device must be accessible in each failure domain.
This leads to the requirement that there be at least three nodes, and that nodes be in three distinct rack or zone failure domains in the case of pre-existing topology labels.
For additional device sets, there must be a storage device, and sufficient resources for the pod consuming it, in each of the three failure domains. Manual placement rules can be used to override default placement rules, but generally this approach is only suitable for bare metal deployments.