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Zyzzyva: Speculative Byzantine Fault Tolerance
 

Summary: 7
Zyzzyva: Speculative Byzantine
Fault Tolerance
RAMAKRISHNA KOTLA
Microsoft Research, Silicon Valley
and
LORENZO ALVISI, MIKE DAHLIN, ALLEN CLEMENT, and EDMUND WONG
The University of Texas at Austin
A longstanding vision in distributed systems is to build reliable systems from unreliable com-
ponents. An enticing formulation of this vision is Byzantine Fault-Tolerant (BFT) state machine
replication, in which a group of servers collectively act as a correct server even if some of the servers
misbehave or malfunction in arbitrary ("Byzantine") ways. Despite this promise, practitioners hes-
itate to deploy BFT systems, at least partly because of the perception that BFT must impose high
overheads.
In this article, we present Zyzzyva, a protocol that uses speculation to reduce the cost of BFT
replication. In Zyzzyva, replicas reply to a client's request without first running an expensive three-
phase commit protocol to agree on the order to process requests. Instead, they optimistically adopt
the order proposed by a primary server, process the request, and reply immediately to the client.
If the primary is faulty, replicas can become temporarily inconsistent with one another, but clients
detect inconsistencies, help correct replicas converge on a single total ordering of requests, and

  

Source: Alvisi, Lorenzo - Department of Computer Sciences, University of Texas at Austin

 

Collections: Computer Technologies and Information Sciences