DCA Question #44: Real Exam Question with Answer & Explanation

Question

Which of these swarm manager configurations will cause the cluster to be in a lost quorum state?

Options

• A4 managers of which 2 are healthy
• B1 manager of which 1 is healthy
• C3 managers of which 2 are healthy
• D5 managers of which 3 are healthy

Explanation

A Docker Swarm cluster enters a lost quorum state when more than half of its manager nodes become unavailable, preventing the cluster from reaching consensus.

Common mistakes.

• B. A single manager node, if healthy, maintains its own quorum (1/2 + 1 = 1).
• C. For 3 managers, the quorum is (3/2) + 1 = 2 (rounding up to the next integer for the majority). With 2 healthy managers, the quorum is maintained.
• D. For 5 managers, the quorum is (5/2) + 1 = 3 (rounding up). With 3 healthy managers, the quorum is maintained.

Concept tested. Docker Swarm quorum requirements

Reference. https://docs.docker.com/engine/swarm/admin_guide/#manager-availability

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