TY - GEN

T1 - Limitations of highly-available eventually-consistent data stores

AU - Attiya, Hagit

AU - Ellen, Faith

AU - Morrison, Adam

N1 - Publisher Copyright:
© Copyright 2015 ACM.

PY - 2015/7/21

Y1 - 2015/7/21

N2 - Modern replicated data stores aim to provide high availability, by immediately responding to client requests, often by implementing objects that expose concurrency. Such objects, for example, multi-valued registers (MVRs), do not have sequential specifications. This paper explores a recent model for replicated data stores that can be used to precisely specify causal consistency for such objects, and liveness properties like eventual consistency, without revealing details of the underlying implementation. The model is used to prove the following results: An eventually consistent data store implementing MVRs cannot satisfy a consistency model strictly stronger than observable causal consistency (OCC). OCC is a model somewhat stronger than causal consistency, which captures executions in which client observations can use causality to infer concurrency of operations. This result holds under certain assumptions about the data store. Under the same assumptions, an eventually consistent and causally consistent replicated data store must send messages of unbounded size: If s objects are supported by n replicas, then, for every k > 1, there is an execution in which an (minfn; sgk)-bit message is sent.

AB - Modern replicated data stores aim to provide high availability, by immediately responding to client requests, often by implementing objects that expose concurrency. Such objects, for example, multi-valued registers (MVRs), do not have sequential specifications. This paper explores a recent model for replicated data stores that can be used to precisely specify causal consistency for such objects, and liveness properties like eventual consistency, without revealing details of the underlying implementation. The model is used to prove the following results: An eventually consistent data store implementing MVRs cannot satisfy a consistency model strictly stronger than observable causal consistency (OCC). OCC is a model somewhat stronger than causal consistency, which captures executions in which client observations can use causality to infer concurrency of operations. This result holds under certain assumptions about the data store. Under the same assumptions, an eventually consistent and causally consistent replicated data store must send messages of unbounded size: If s objects are supported by n replicas, then, for every k > 1, there is an execution in which an (minfn; sgk)-bit message is sent.

KW - Causal consistency

KW - Eventual consistency

KW - Replicated data store

UR - http://www.scopus.com/inward/record.url?scp=84957667360&partnerID=8YFLogxK

U2 - 10.1145/2767386.2767419

DO - 10.1145/2767386.2767419

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AN - SCOPUS:84957667360

T3 - Proceedings of the Annual ACM Symposium on Principles of Distributed Computing

SP - 385

EP - 394

BT - PODC 2015 - Proceedings of the 2015 ACM Symposium on Principles of Distributed Computing

PB - Association for Computing Machinery

T2 - ACM Symposium on Principles of Distributed Computing, PODC 2015

Y2 - 21 July 2015 through 23 July 2015

ER -