Questions tagged [fault-tolerance]

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How to detect a consensus is BFT or not?

Can we divide consensus algorithms into BFT (Byzantine Fault Tolerant) and non-BFT ? If so, How to detect a consensus is BFT or non-BFT ? Is there any non-BFT consensus algorithm example ?
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Why don't RDBMS use a quorum based solution to do failover

For RDBMS viz. MySql, PostgreSql a common solution for scalability and high availability is to run a primary instance as master that is a read-write instance and one or more read replicas. If the ...
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959 views

Why does RAID-5 require an additional disk for parity blocks?

I know that RAID-5 consists of block-level striping across multiple disks, but using an additional parity-check block on each disk .. and that at least two disks are required for striping. And it's ...
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Enforcing application layer consensus on top of a distributed consensus protocol

If I understand correctly, the term "consensus" in distributed consensus algorithms means that all the participants ("peers") achieve a common understanding of some data value. Different algorithms ...
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Is there a usable implementation of PBFT? [closed]

In the original Practical Byzantine Fault Tolerance (PBFT) paper they mention they implemented a fault tolerant NFS service. To do that they made a library for PBFT. Does that exist anywhere? As that ...
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What is the algorithm for Blockchain's Byzantine Fault Tolerance?

This person was asked: "Why is a blockchain implementation different than a distributed consensus system like Raft?" In part of their answer they replied: For one, Raft is not Byzantine fault ...
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Why/how are the banking systems that robust?

I'm a developer, so I understand (a bit) how computers work, and how softwares work and fail. In all softwares I've dealt with (as a developer or as a user), I've always seen small or huge bugs: ...
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1answer
452 views

Impossibility for Byzantine Generals Problem where $n \leq 3m$

Wiki: https://en.wikipedia.org/wiki/Byzantine_fault_tolerance In the paper "Reaching Agreement in the Presence of Faults", M. Pease et al. proved that there is no protocol (of some kind) to solve the ...
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Why are directed graphs important?

We have been reading about algorithms for MST, strong-connectivity, routing, etc. in directed graphs. Also recently people have been doing research for dynamic and fault tolerant algorithms for ...
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1answer
99 views

How does the Weibull distribution work as fault model in wireless sensor networks?

I am a little bit confused with the concept of using the Weibull distribution or other distribution for fault model. As I understand, in simulation this distribution is often used for modelling a ...
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2answers
809 views

Byzantine generals problem with signed messages (Lamport)

I have some trouble understanding Lamport's paper about the Byzantine generals problem when it comes to signed messages. He showed that, with signed messages, the number of generals must be at least $...
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1answer
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How P2P search engines prevent corruption of distributed index by malicious peers?

As a hobby, I am writing a simple and primitive distributed web search engine. It occurred to me that it currently has no protection against malicious peers trying to skew the search results. The ...
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Iterative Byzantine consensus in directed graphs with unbounded malicious nodes

I've found many articles describing iterative procedures to reach Byzantine agreement on a graph (for instance http://www.crhc.illinois.edu/wireless/papers/icdcn14-vaidya.pdf or http://arxiv.org/pdf/...
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Three phase commit : study case

Consider a group of five processors implementing three-phase commit protocol. During the execution of the protocol, the coordinator and one other process crash. Two of the remaining processes are ...
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2answers
533 views

How does FDS (flat datacenter storage) make optimizations around locality unnecessary?

I was reading the following computer systems paper: https://www.usenix.org/system/files/conference/osdi12/osdi12-final-75.pdf And I was trying to understand why it claims that it does not need data ...
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1answer
994 views

Lamport's Byzantine Generals Algorithm

I've stumbled at the first OralMessage algorithm in Lamport, et al's paper. I've searched the web and there are dozens of sites, restating in exactly the same terms and examples, which isn't helping ...
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1answer
831 views

Impossibility condition in the Byzantine Generals problem

I am unable to understand why there is a requirement of 3m+1 generals overall given m traitors. As per my understanding, the steps are as follows: Each general decides a strategy and forwards their ...
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What if the electricity goes off while a file is being renamed?

Suppose I'm renaming a file and the electricity goes off right in the middle. Naively, it looks like the file could be in some “half-renamed” state. Maybe the name would have half the old name and ...
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Message receipt verification in a cluster

At my current project I had a network problem come up for which I could not find a solution. In a peer-to-peer network I needed to send an action to all peers, and each peer was to act on it only if ...