Fast Paxos

Paxos review

  • Round structure
  • Discover the possibly chosen value of previous rounds?
    • no value accepted before
    • a single round or multiple round accepted before
      • choose the higher round
      • is there a single value or multiple accepted in this round?
  • Trick, intersect
    • What if increasing the prepare quorum size?
    • What if increasing the accept quorum size?
  • The high performance model
    • there is a leader
    • client to leader
    • leader send to follwers, and followers ack
    • leader reply to client
    • 2 RTT in total
  • Question: can we reduce RTT?
    • client directly send to every one?

Fastpath Quorum

  • problem
    • multiple values can be accepted in a round
  • quorum size: a majority?
    • how to recover in the next round?
    • compare number is no longer possible
  • quorum size: all?
    • if see differeent values, then values chosen
    • unless see the overlap between N and M, which is M, no need to accept this value
  • what is the right size? between M and N?
  • problem, the intersection of M and Qf does not intersect with another QF
    • Make the intesect!
    • Qf+M-N+Qf-N>0 2Qf+M>2N
      • N-E+N-F-N+N-E-N>0, N>2E+F
    • 2M>N
      • N-F+N-F>N, N>2F
    • 4Qf>=3N,