Why it matters

Split brain is a top cause of distributed data loss. Understanding prevents design flaws.

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The architecture

Cause: network partition disconnects cluster into groups.

Symptom: multiple sides accept writes independently.

Split brain scenarioNetwork partitioncluster splitsBoth sides activedual writesDivergence on mergecorruptionQuorum (majority) required to write prevents split brain: minority side can't write
Split brain mechanism.
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How it works end to end

Prevention: quorum-based writes. Require majority (N/2 + 1) to commit. Minority side can't write.

Fencing: force minority side offline. STONITH (Shoot The Other Node In The Head).

Consensus (Raft, Paxos): natively require quorum.

Detection: monitor for quorum loss.