Choose whether cluster anti-affinity should yield during a node outage

Source facts

Microsoft uses anti-affinity to try to keep selected roles on different nodes. The AntiAffinityClassNames setting is a soft constraint; the documentation also describes enforcing a hard separation. Microsoft warns that, in a two-node configuration with enforced anti-affinity, losing one node means both separated groups cannot run. Microsoft documentation.

Applicability

Identify the roles, their resource demand, available nodes, and service priorities. Ask workload owners whether maintaining separation or keeping both services running should take precedence during reduced capacity.

DSE recommendation

Record that tradeoff before choosing the anti-affinity setting. Name the roles that belong to the same separation class and define the accepted outage behavior. Have the cluster owner review capacity and the application owners approve any intentional loss of service under enforcement.

Verification

Inspect the configured class values and observe placement under normal conditions. In an approved maintenance test, remove one eligible node and compare the resulting role state with the decision. Preserve an unavailable role as an expected or unexpected outcome explicitly; do not equate policy enforcement with application availability.

Official references

Microsoft Learn: Cluster affinity. Source reviewed September 8, 2026.