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Created December 13, 2018 22:56
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Final Review - DistSys Lecture - Dec 13th, 2018

Paxos

MultiPaxos

MultiPaxos is used for consensus on a log of values

Paxos vs. Raft

Raft is bad when there’s leader instability

Consistency Model

Linearizability

  • Everything happens in actual time

Sometimes represented as lines with duration — The effect of the write or read operation can take place

Sequential

  • Every replica has the same value (when it write is applied, it applies to all processes/replicas)
  • Writes can be delayed relative to other nodes

Causal

  • Causality

Eventual

Fingertables (Distributed Hashtables)

Broadcasting

Many nodes are broadcasting messages to each other. How do we order the messages?

Total Ordering

All the nodes agree on the same order of messages, always. Any other ordering is a partial ordering.

FIFO Ordering

Messages from the same node will be in ordered sequentially

IS-IS algorithm

Provides total ordering by distributing the responsibility of sequencing messages (probably not going to go in-depth in the final)

Byzantium (Lieutenants & Commander)

The total number of nodes must be 3 times the number of traitors

Bitcoin!

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