2014 | OriginalPaper | Chapter
Separating Data and Control: Asynchronous BFT Storage with 2t + 1 Data Replicas
Authors : Christian Cachin, Dan Dobre, Marko Vukolić
Published in: Stabilization, Safety, and Security of Distributed Systems
Publisher: Springer International Publishing
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The overhead of Byzantine fault tolerant (BFT) storage is a primary concern that prevents its adoption in practice. The cost stems from the need to maintain at least 3
t
+ 1 copies of the data at different storage replicas in the asynchronous model, so that
t
Byzantine replica faults can be tolerated. This paper presents
MDStore
, the first fully asynchronous BFT storage protocol that reduces the number of replicas that store the payload data to as few as 2
t
+ 1 and maintains metadata at 3
t
+ 1 replicas on (possibly) different servers. At the heart of
MDStore
lies a metadata service built upon a new abstraction called “timestamped storage.” Timestamped storage allows for conditional writes (facilitating the implementation of the metadata service) and has consensus number one (making it implementable with wait-free semantics in an asynchronous system despite faults). In addition to its low replication overhead,
MDStore
offers strong guarantees by emulating a multi-writer multi-reader atomic register, providing wait-free termination, and tolerating any number of Byzantine readers and crash-faulty writers.