Titre:	Replicação máquina de estados paralela com escalonamento híbrido
Auteur(s):	Burgos, Aldênio de Vilaça
Orientador(es)::	Alchieri, Eduardo Adilio Pelinson
Assunto::	Replicação máquina de estados paralela Replicação máquina de estados Blockchain
Date de publication:	8-déc-2021
Data de defesa::	17-sep-2021
Référence bibliographique:	BURGOS, Aldênio de Vilaça. Replicação máquina de estados paralela com escalonamento híbrido. 2021. 84 f., il. Dissertação (Mestrado em Informática)—Universidade de Brasília, Brasília, 2021.
Abstract:	The growing demand for reliable applications with ever lower response times has been driving research on the performance of fault-tolerant services for several years. We know that designing fault-tolerant applications is critical, but it is not enough. A trusted application whose response time exceeds the (ever-shorter) tolerance of its customers can be just as destructive to the business as an untrusted application. The State Machine Replication (SMR) technique, launched in 1990 and widely used in the implementation of reliable services, brings with it a side effect. In its classic form, it eliminates any kind of concurrency or parallelism in fulfilling customer requests. For years, the main microprocessor manufacturers have been looking to increase the performance of their equipment, by increasing their parallelism capacity, adding more and more cores to their multi-core architectures. That is, in an increasingly parallel world, the sequential behavior of classical SMR has become a serious disadvantage. This paved the way for a vast research effort to improve the performance of these replicated services, and thus came Parallel State Machine Replication (PSMR). In the last two decades, new techniques, algorithms and studies have emerged in or- der to improve PSMR. A key aspect of these solutions is how to schedule client requests in order to allow a part of them to be executed in parallel in the service’s replicas. In this context, this master’s dissertation proposes an PSMR approach that uses a hybrid scheduling method, with the objective of increasing the system performance by increas- ing its parallelism. The developed method is called hybrid because it derives from the improvement of a combination of two prominent scheduling methods for earlier PSMR, Early and Late. The former performs excellently with non-conflicting workloads, but this performance drops off sharply as we increase the conflict rate. 1 The second, which surpasses the first as the conflict rate grows,2 has a performance limiting factor in its operation when the conflict rate is reduced. We demonstrated in the tests carried out that the proposed approach performed better than its predecessors, in addition to eliminating its main limitations. 1The percentage of conflicts is inversely proportional to the opportunities for parallelism between operations. 2Up to a certain limit, as very high conflict rates indicate typically sequential workloads. viii A case study was also carried out on the application of an PSMR, with the proposed scheduling method, in Blockchain systems.
metadata.dc.description.unidade:	Instituto de Ciências Exatas (IE) Departamento de Ciência da Computação (IE CIC)
Description:	Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, 2021.
metadata.dc.description.ppg:	Programa de Pós-Graduação em Informática
Licença::	A concessão da licença deste item refere-se ao termo de autorização impresso assinado pelo autor com as seguintes condições: Na qualidade de titular dos direitos de autor da publicação, autorizo a Universidade de Brasília e o IBICT a disponibilizar por meio dos sites www.bce.unb.br, www.ibict.br, http://hercules.vtls.com/cgi-bin/ndltd/chameleon?lng=pt&skin=ndltd sem ressarcimento dos direitos autorais, de acordo com a Lei nº 9610/98, o texto integral da obra disponibilizada, conforme permissões assinaladas, para fins de leitura, impressão e/ou download, a título de divulgação da produção científica brasileira, a partir desta data.
Collection(s) :	Teses, dissertações e produtos pós-doutorado

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