consensus

  • Reading Group. Near-Optimal Latency Versus Cost Tradeoffs in Geo-Distributed Storage

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    Short Summary Yesterday we discussed Pando, a geo-replication system achieving near-optimal latency-cost tradeoff in storage systems. Pando uses large Flexible Paxos deployments and erasure coding to do its magic. Pando relies on having many storage sites to locate sites closer to users. It then uses Flexible Paxos to optimize read and write quorums to have…

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  • Reading Group. RMWPaxos: Fault-Tolerant In-Place Consensus Sequences

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    Quick Summary In the last reading group discussion, we talked about RMWPaxos. The paper argues that under some circumstances, log-based replication schemes and replicated state machines (RSMs), like Multi-Paxos, are a waste of resources. For example, when the state is small, it may be more efficient to just manage the state directly instead of managing…

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  • One Page Summary. Gryff: Unifying Consensus and Shared Registers

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    This paper by Matthew Burke, Audrey Cheng, and Wyatt Lloyd appeared in NSDI 2020 and explores an interesting idea of a hybrid replication protocol. The premise is very simple – we can take one protocol that solves a part of the problem well, and marry it with another protocol that excels at the second half…

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  • PigPaxos: continue devouring communication bottlenecks in distributed consensus.

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    This is a short follow-up to Murat’s PigPaxos post. I strongly recommend reading it first as it provides full context for what is to follow. And yes, it also includes the explanation of what pigs have to do with Paxos. Short Recap of PigPaxos. In our recent SIGMOD paper we looked at the bottleneck of…

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  • One Page Summary. Aegean: Replication beyond the client-server model

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    One Page Summary.  Aegean: Replication beyond the client-server model This paper builds o n a key observation about the operation of complex distributed applications. Namely, microservice style of application rarely follows a simple client-server architecture, where a client makes a request and the server (or servers) respond to a request. Instead, many applications often use…

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  • One Page Summary: Ring Paxos

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    This paper (Ring Paxos: A high-throughput atomic broadcast protocol) has been out for quite some time, but it addresses a problem still relevant in many distributed consensus protocols. Ring Paxos aims to reduce the communication load in the Paxos cluster and provide better scalability. As we have shown in our SIGMOD 2019 paper, communication is…

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  • A Few Words about Inconsistent Replication (IR)

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    Recently I was reading the “Building Consistent Transaction with Inconsistent Replication” paper. In this paper authors use inconsistently replicated state machine, but yet they are capable of creating a consistent transaction system. So what is Inconsistent Replication (IR)? In the previous posts I summarized Raft and EPaxos. These two algorithms are used to achieve consensus…

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  • EPaxos: Consensus with no leader

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    In my previous post I talked about Raft consensus algorithm. Raft has a strong leader which may present some problems under certain circumstances, for example in case of leader failure or when deployed over a wide area network (WAN). Egalitarian Paxos, or EPaxos, discards the notion of a leader and allows each node to be…

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  • Consensus with Raft Algorithm

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    When we talk about consensus in a distributed system, we talk about a system consisting of multiple machines that act as one state machine yet capable of surviving failures of some of the system nodes. Consensus algorithms are designed to enforce all distributed nodes have the same state so that the distributed system can tolerate…

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