PAXOS Concensus Protocol vs 2PC & 3PC

PAXOS is used by Google's Chubby, Apache Zookeeper, and FoundationDB

Majority Concensus

http://the-paper-trail.org/blog/consensus-protocols-paxos/

If the leader is relatively stable, phase 1 becomes unnecessary. Thus, it is possible to skip phase 1 for future instances of the protocol with the same leader.
Multi-Paxos reduces the failure-free message delay (proposal to learning) from 4 delays to 2 delays.

2PC

The greatest disadvantage of the two-phase commit protocol is that it is a blocking protocol. If the coordinator fails permanently, some cohorts will never resolve their transactions: After a cohort has sent an agreement message to the coordinator, it will block until a commit or rollback is received.

 3PC
The main disadvantage to this algorithm is that it cannot recover in the event the network is segmented in any manner. The original 3PC algorithm assumes a fail-stop model, where processes fail by crashing and crashes can be accurately detected, and does not work with network partitions or asynchronous communication.
Keidar and Dolev's E3PC[2] algorithm eliminates this disadvantage.
The protocol requires at least 3 round trips to complete, needing a minimum of 3 round trip times (RTTs). This is potentially a long latency to complete each transaction.

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