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,