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ADR 0017: HA requires at least 3 votes; with 2 nodes Quoro tells the user and offers a witness

  • Status: Accepted
  • Date: 2026-11-02
  • Ledger id: D-0017
  • Tags: reliability, witness
  • Supersedes: none
  • Superseded by: none
  • Related: none

Context

Majority voting needs an odd number of voters; the witness only breaks ties and stores no data.

Decision

HA requires at least 3 votes; with 2 nodes Quoro tells the user and offers a witness.

Witness options: (1) lightweight free daemon on any machine, must be in a different failure domain than the nodes (a home PC next to node A fails together with it); (2) optional external lease arbiter: Cloudflare Durable Object (strong consistency) or S3/R2 conditional writes (to verify). The self-hosted witness is free and first-class.

Some wording was changed for the public repository.

Consequences

  • This decision is binding for all contributors and agents. Changing it requires a new ADR approved by the maintainer (see ADR 0036).

Generated from decision D-0017 in the project decision ledger. Do not edit by hand; changes go through a new decision.